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Bisht A, Goh KKT, Sims IM, Edwards PJB, Matia-Merino L. Does harvesting age matter? Changes in structure and rheology of a shear-thickening polysaccharide from Cyathea medullaris as a function of age. Carbohydr Polym 2024; 329:121757. [PMID: 38286538 DOI: 10.1016/j.carbpol.2023.121757] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2023] [Revised: 12/21/2023] [Accepted: 12/28/2023] [Indexed: 01/31/2024]
Abstract
A shear-thickening polysaccharide from the New Zealand Black tree fern (Cyathea medullaris, commonly known as mamaku) extracted from different age fronds (stage 1: young, stage 2: fully grown and stage 3: old) was characterised in terms of structure and rheological properties. Constituent sugar analysis and 1H and 13C NMR revealed a repeating backbone of -4)-β-D-GlcpA-(1 → 2)-α-D-Manp-(1→, for all mamaku polysaccharide (MP) samples from different age fronds without any alterations in molecular structure. However, the molecular weight (Mw) was reduced with increasing age, from ~4.1 × 106 to ~2.1 × 106 Da from stage 1 to stage 3, respectively. This decrease in Mw (and size) consequently reduced the shear viscosity (ηs-Stage 1 > ηs-Stage 2 > ηs-Stage 3). However, the extent of shear-thickening and uniaxial extensional viscosity of MP stage 2 was greater than MP stage 1, which was attributed to a greater intermolecular interaction occurring in the former. Shear-thickening behaviour was not observed in MP stage 3.
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Affiliation(s)
- Akshay Bisht
- School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand.
| | - Kelvin K T Goh
- School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand.
| | - Ian M Sims
- The Ferrier Research Institute, Victoria University of Wellington, New Zealand.
| | - Patrick J B Edwards
- School of Natural Sciences, Massey University, Palmerston North, New Zealand.
| | - Lara Matia-Merino
- School of Food and Advanced Technology, Massey University, Palmerston North, New Zealand.
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2
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Garavís M, Edwards PJB, Serrano-Chacón I, Doluca O, Filichev V, González C. Understanding intercalative modulation of G-rich sequence folding: solution structure of a TINA-conjugated antiparallel DNA triplex. Nucleic Acids Res 2024; 52:2686-2697. [PMID: 38281138 PMCID: PMC10954471 DOI: 10.1093/nar/gkae028] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Revised: 12/21/2023] [Accepted: 01/06/2024] [Indexed: 01/30/2024] Open
Abstract
We present here the high-resolution structure of an antiparallel DNA triplex in which a monomer of para-twisted intercalating nucleic acid (para-TINA: (R)-1-O-[4-(1-pyrenylethynyl)phenylmethyl]glycerol) is covalently inserted as a bulge in the third strand of the triplex. TINA is a potent modulator of the hybridization properties of DNA sequences with extremely useful properties when conjugated in G-rich oligonucleotides. The insertion of para-TINA between two guanines of the triplex imparts a high thermal stabilization (ΔTM = 9ºC) to the structure and enhances the quality of NMR spectra by increasing the chemical shift dispersion of proton signals near the TINA location. The structural determination reveals that TINA intercalates between two consecutive triads, causing only local distortions in the structure. The two aromatic moieties of TINA are nearly coplanar, with the phenyl ring intercalating between the flanking guanine bases in the sequence, and the pyrene moiety situated between the Watson-Crick base pair of the two first strands. The precise position of TINA within the triplex structure reveals key TINA-DNA interactions, which explains the high stabilization observed and will aid in the design of new and more efficient binders to DNA.
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Affiliation(s)
- Miguel Garavís
- Instituto de Química Física ‘Blas Cabrera’, (IQF-CSIC), Madrid 28006, Spain
| | - Patrick J B Edwards
- School of Natural Sciences, Massey University, Palmerston North 4412, New Zealand
| | | | - Osman Doluca
- School of Natural Sciences, Massey University, Palmerston North 4412, New Zealand
| | | | - Carlos González
- Instituto de Química Física ‘Blas Cabrera’, (IQF-CSIC), Madrid 28006, Spain
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3
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Harjes E, Edwards PJB, Bisset SW, Patchett ML, Jameson GB, Yang SH, Navo CD, Harris PWR, Brimble MA, Norris GE. NMR Shows Why a Small Chemical Change Almost Abolishes the Antimicrobial Activity of Glycocin F. Biochemistry 2023; 62:2669-2676. [PMID: 37531216 DOI: 10.1021/acs.biochem.3c00197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
Glycocin F (GccF), a ribosomally synthesized, post-translationally modified peptide secreted by Lactobacillus plantarum KW30, rapidly inhibits the growth of susceptible bacteria at nanomolar concentrations. Previous studies have highlighted structural features important for its activity and have shown the absolute requirement for the Ser18 O-linked GlcNAc on the eight-residue loop linking the two short helices of the (C-X6-C)2 structure. Here, we show that an ostensibly very small chemical modification to Ser18, the substitution of the Cα proton with a methyl group, reduces the antimicrobial activity of GccF 1000-fold (IC50 1.5 μM cf. 1.5 nM). A comparison of the GccFα-methylSer18 NMR structure (PDB 8DFZ) with that of the native protein (PDB 2KUY) showed a marked difference in the orientation and mobility of the loop, as well as a markedly different positioning of the GlcNAc, suggesting that loop conformation, dynamics, and glycan presentation play an important role in the interaction of GccF with as yet unknown but essential physiological target molecules.
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Affiliation(s)
- Elena Harjes
- School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Patrick J B Edwards
- School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
| | - Sean W Bisset
- School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Mark L Patchett
- School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
| | - Geoffrey B Jameson
- School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
| | - Sung-Hyun Yang
- School of Chemical Sciences, The University of Auckland, 23 Symonds St, Auckland 1142, New Zealand
| | - Claudio D Navo
- School of Chemical Sciences, The University of Auckland, 23 Symonds St, Auckland 1142, New Zealand
| | - Paul W R Harris
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- School of Chemical Sciences, The University of Auckland, 23 Symonds St, Auckland 1142, New Zealand
| | - Margaret A Brimble
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
- School of Chemical Sciences, The University of Auckland, 23 Symonds St, Auckland 1142, New Zealand
| | - Gillian E Norris
- School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand
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4
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Mohandas N, Edwards PJB, Kent LM, Jameson GB, Williams MAK. Biotinylation of reducing and non-reducing termini to create plug-and-play polysaccharides. Carbohydr Polym 2023; 305:120569. [PMID: 36737207 DOI: 10.1016/j.carbpol.2023.120569] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2022] [Revised: 12/14/2022] [Accepted: 01/05/2023] [Indexed: 01/11/2023]
Abstract
Single-molecule studies continue to grow in popularity. In cases where biopolymer samples of interest exhibit variations in fine-structure between individual chains such single-molecule studies uniquely offer the promise of revealing deep structure-function relationships. Polysaccharides are typically studied in bulk and, as such, their study could greatly benefit from the application of single-molecule techniques. However, while for example single-molecule optical tweezers (OT) studies have become commonplace for DNA, studies of polysaccharides have lagged behind somewhat, complicated by the difficulty of studying molecules that amongst other things have more complex end-group chemistry. Recently, divalent streptavidin linkers have been shown to be capable of concatenating two pieces of biotin-terminated DNA to produce robust composite strings that run intact through conventional gels, and can be used in single-molecule OT experiments (Mohandas, Kent, Raudsepp, Jameson, & Williams, 2022). By using two such streptavidin linkers, biotin-terminated polymers could be inserted between two sections of DNA in order to facilitate single-molecule experiments on biopolymers that are currently difficult to address by other means. Here, we describe a generic approach for placing the required biotin moieties at both ends of polysaccharide chains, producing plug-and-play polysaccharide inserts that can be incorporated into composite polymer strings using streptavidin linking hubs.
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Affiliation(s)
- Nimisha Mohandas
- School of Natural Sciences, Massey University, Palmerston North, New Zealand; Riddet Institute, Massey University, Palmerston North, New Zealand
| | - Patrick J B Edwards
- School of Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Lisa M Kent
- School of Natural Sciences, Massey University, Palmerston North, New Zealand
| | - Geoffrey B Jameson
- School of Natural Sciences, Massey University, Palmerston North, New Zealand; Riddet Institute, Massey University, Palmerston North, New Zealand; MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand
| | - Martin A K Williams
- School of Natural Sciences, Massey University, Palmerston North, New Zealand; Riddet Institute, Massey University, Palmerston North, New Zealand; MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, New Zealand.
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5
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Varnava KG, Edwards PJB, Cameron AJ, Harjes E, Sarojini V. Cyclic peptides bearing the d-Phe-2-Abz turn motif: Structural characterization and antimicrobial potential. J Pept Sci 2020; 27:e3291. [PMID: 33283398 DOI: 10.1002/psc.3291] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2020] [Revised: 10/07/2020] [Accepted: 10/14/2020] [Indexed: 11/10/2022]
Abstract
The effect on secondary structure and antimicrobial activity of introducing different cyclic constraints in linear β-hairpin antimicrobial peptides has been investigated with the intention of generating cyclic β sheets as promising antimicrobials with improved therapeutic potential. The linear peptides were cyclized head to tail either directly or after the addition of either a second turn motif or a disulfide bridge. The propensity of these peptides to adopt a cyclic β-sheet structure has been correlated to their antibacterial activity. All cyclic peptides showed enhanced activity, compared with their linear counterparts against methicillin-resistant Staphylococcus aureus. Scanning electron microscopy and transmission electron microscopy studies showed that this family kills bacteria through membrane lysis. The peptide that showed the best efficacy against all strains (exhibiting nanomolar activity), while retaining low haemolysis, bears two symmetrical, homochiral d-phe-2-Abz-d-ala turns and adopted a flexible structure. Its twin peptide that bears heterochiral turns (one with d-ala and one with L-Ala) showed reduced antibacterial activity and higher percentage of haemolysis. Circular dichroism and nuclear magnetic resonance spectroscopy indicate that heterochirality in the two turns leads to oligomerization of the peptide at higher concentrations, stabilizing the β-sheet secondary structure. More rigid secondary structure is associated with lower activity against bacteria and loss of selectivity.
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Affiliation(s)
- Kyriakos G Varnava
- School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand
| | - Patrick J B Edwards
- School of Fundamental Sciences, Massey University, Palmerston North, 4442, New Zealand.,Maurice Wilkins Centre for Molecular BioDiscovery, Auckland, 1142, New Zealand
| | - Alan J Cameron
- School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand.,Maurice Wilkins Centre for Molecular BioDiscovery, Auckland, 1142, New Zealand
| | - Elena Harjes
- School of Fundamental Sciences, Massey University, Palmerston North, 4442, New Zealand.,Maurice Wilkins Centre for Molecular BioDiscovery, Auckland, 1142, New Zealand
| | - Vijayalekshmi Sarojini
- School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand.,The MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, 6140, New Zealand
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6
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Harjes E, Jameson GB, Tu YH, Burr N, Loo TS, Goroncy AK, Edwards PJB, Harjes S, Munro B, Göbl C, Sattlegger E, Norris GE. Experimentally based structural model of Yih1 provides insight into its function in controlling the key translational regulator Gcn2. FEBS Lett 2020; 595:324-340. [PMID: 33156522 DOI: 10.1002/1873-3468.13990] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2020] [Revised: 10/21/2020] [Accepted: 11/02/2020] [Indexed: 12/15/2022]
Abstract
Yeast impact homolog 1 (Yih1), or IMPACT in mammals, is part of a conserved regulatory module controlling the activity of General Control Nonderepressible 2 (Gcn2), a protein kinase that regulates protein synthesis. Yih1/IMPACT is implicated not only in many essential cellular processes, such as neuronal development, immune system regulation and the cell cycle, but also in cancer. Gcn2 must bind to Gcn1 in order to impair the initiation of protein translation. Yih1 hinders this key Gcn1-Gcn2 interaction by binding to Gcn1, thus preventing Gcn2-mediated inhibition of protein synthesis. Here, we solved the structures of the two domains of Saccharomyces cerevisiae Yih1 separately using Nuclear Magnetic Resonance and determined the relative positions of the two domains using a range of biophysical methods. Our findings support a compact structural model of Yih1 in which the residues required for Gcn1 binding are buried in the interface. This model strongly implies that Yih1 undergoes a large conformational rearrangement from a latent closed state to a primed open state to bind Gcn1. Our study provides structural insight into the interactions of Yih1 with partner molecules.
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Affiliation(s)
- Elena Harjes
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Maurice Wilkins Centre for Molecular BioDiscovery, Massey University, Palmerston North, New Zealand
| | - Geoffrey B Jameson
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Maurice Wilkins Centre for Molecular BioDiscovery, Massey University, Palmerston North, New Zealand
| | - Yi-Hsuan Tu
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Natalie Burr
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Trevor S Loo
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Alexander K Goroncy
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Patrick J B Edwards
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Stefan Harjes
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Ben Munro
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Christoph Göbl
- Centre for Free Radical Research, Department of Pathology, University of Otago, Christchurch, New Zealand
| | - Evelyn Sattlegger
- Maurice Wilkins Centre for Molecular BioDiscovery, Massey University, Palmerston North, New Zealand.,School of Natural and Computational Sciences, Massey University, Auckland, New Zealand
| | - Gillian E Norris
- School of Fundamental Sciences, Massey University, Palmerston North, New Zealand.,Maurice Wilkins Centre for Molecular BioDiscovery, Massey University, Palmerston North, New Zealand
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7
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Su Y, Edwards PJB, Stetsenko DA, Filichev VV. The Importance of Phosphates for DNA G-Quadruplex Formation: Evaluation of Zwitterionic G-Rich Oligodeoxynucleotides. Chembiochem 2020; 21:2455-2466. [PMID: 32281223 DOI: 10.1002/cbic.202000110] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2020] [Revised: 04/09/2020] [Indexed: 12/21/2022]
Abstract
A quaternary ammonium butylsulfonyl phosphoramidate group (N+) was designed to replace all the phosphates in a G-rich oligodeoxynucleotide d(TG4 T), resulting in a formally charge-neutral zwitterionic N+TG4 T sequence. We evaluated the effects of N+phosphate modifications on the structural, thermodynamic and kinetic properties of the parallel G-quadruplexes (G4) formed by TG4 T and compared them to the properties of the recently published phosphoryl guanidine d(TG4 T) (PG-TG4 T). Using size-exclusion chromatography, we established that, unlike PG-TG4 T, which exists as a mixture of complexes of different molecularity in solution, N+TG4 T forms an individual tetramolecular complex. In contrast to PG modifications that destabilized G4s, the presence of N+ modifications increased thermal stability relative to unmodified [d(TG4 T)]4 . The initial stage of assembly of N+TG4 T proceeded faster in the presence of Na+ than K+ ions and, similarly to PG-TG4 T, was independent of the salt concentration. However, after complex formation exceeded 75 %, N+TG4 T in solution with Na+ showed slower association than with K+ . N+TG4 T could also form G4s in solution with Li+ ions at a very low strand concentration (10 μM); something that has never been reported for the native d(TG4 T). Charge-neutral PG-G4s can invade preformed native G4s, whereas no invasion was observed between N+and native G4s, possibly due to the increased thermal stability of [N+TG4 T]4 . The N+ modification makes d(TG4 T) fully resistant to enzymatic digestion, which could be useful for intracellular application of N+-modified DNA or RNA.
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Affiliation(s)
- Yongdong Su
- School of Fundamental Sciences, Massey University, Private Bag 11-222, 4442, Palmerston North, New Zealand
| | - Patrick J B Edwards
- School of Fundamental Sciences, Massey University, Private Bag 11-222, 4442, Palmerston North, New Zealand
| | - Dmitry A Stetsenko
- Novosibirsk State University, 2 Pirogov Street, Novosibirsk, 630090, Russia.,Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, 10 Lavrentiev Avenue, Novosibirsk, 630090, Russia
| | - Vyacheslav V Filichev
- School of Fundamental Sciences, Massey University, Private Bag 11-222, 4442, Palmerston North, New Zealand.,Maurice Wilkins Centre for Molecular Biodiscovery, Auckland, 1142, New Zealand
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8
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Leung YB, Cave NJ, Heiser A, Edwards PJB, Godfrey AJR, Wester T. Metabolic and Immunological Effects of Intermittent Fasting on a Ketogenic Diet Containing Medium-Chain Triglycerides in Healthy Dogs. Front Vet Sci 2020; 6:480. [PMID: 31998762 PMCID: PMC6961514 DOI: 10.3389/fvets.2019.00480] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2019] [Accepted: 12/06/2019] [Indexed: 12/17/2022] Open
Abstract
In several species, intermittent fasting (IF) has been shown to have beneficial effects, including delayed aging, increased lifespan, increased insulin sensitivity, reduced ischemic tissue damage, delayed onset of neurodegenerative disease and improved neuronal repair following injury. However, the metabolic and immunological effects of IF have not been well-established in dogs. The aim of this study was to examine the effects of a 48 h IF regimen using a low fat and a high fat diet in healthy dogs by quantifying the metabolic, hormonal, and immunological changes. We hypothesized that IF dogs would have higher blood ketone and ghrelin concentrations, lower blood leptin, insulin and glucose concentrations, and signs of immunosuppression compared to dogs eating daily. Ten healthy adult dogs were randomized into three group and underwent three feeding regimes in a 3 × 3 Latin square design: twice a day feeding on a low fat (23% energy from fat; LF) diet, 48 h fasting on a low fat diet, and 48 h fasting on a high fat enriched with medium-chain triglycerides (68% energy from fat; HF) diet. Body weight, food intake, activity, blood glucose, β-hydroxybutyrate, leptin, ghrelin, and insulin were measured. Lymphocyte proliferation and neutrophil/macrophage phagocytosis and respiratory burst were measured as markers of immune function. Nuclear magnetic resonance spectroscopy was used to relatively quantify plasma metabolites. When the dogs were IF on a HF diet, they had the highest concentration of blood ketones (mean 0.061 mmol/L, SD 0.024), whereas they had the lowest concentration (mean 0.018 mmol/L, SD 0.004) when fed daily. Blood glucose and insulin concentrations were lower in IF dogs on a HF diet compared to daily feeding or IF on a LF diet. There was an increase in plasma β-hydroxybutyrate concentrations, and a reduction in glucose and insulin concentrations when dogs were IF on a HF diet. There was only a decline in the immune parameters studied when the dogs were IF on a LF diet, which was not seen when on the HF diet. The results of this study indicate the potential of IF to be further investigated as a potential beneficial feeding regime for dogs.
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Affiliation(s)
- Y. Becca Leung
- School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - Nick J. Cave
- School of Veterinary Science, Massey University, Palmerston North, New Zealand
| | - Axel Heiser
- AgResearch, Grasslands Research Centre, Hopkirk Research Institute, Palmerston North, New Zealand
| | | | | | - Tim Wester
- School of Agriculture and Environment, Massey University, Palmerston North, New Zealand
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9
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Lepper CP, Williams MAK, Edwards PJB, Filichev VV, Jameson GB. Effects of Pressure and pH on the Physical Stability of an I‐Motif DNA Structure. Chemphyschem 2019; 20:1567-1571. [DOI: 10.1002/cphc.201900145] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2019] [Revised: 05/01/2019] [Indexed: 12/21/2022]
Affiliation(s)
| | - Martin A. K. Williams
- School of Fundamental Sciences The MacDiarmid Institute and the Riddet InstituteMassey University Palmerston North New Zealand
| | | | | | - Geoffrey B. Jameson
- School of Fundamental Sciences The MacDiarmid Institute and the Riddet InstituteMassey University Palmerston North New Zealand
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10
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Naffa R, Edwards PJB, Norris G. Isolation and characterization of collagen type I crosslink from skin: high-resolution NMR reveals diastereomers of hydroxylysinonorleucine crosslink. Amino Acids 2019; 51:705-715. [PMID: 30788600 DOI: 10.1007/s00726-019-02708-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Accepted: 02/06/2019] [Indexed: 12/24/2022]
Abstract
Skin is made up of mainly collagen type I and its structure is stabilised by the formation of covalent immature and mature crosslinks. In this study, collagen immature crosslink hydroxylysinonorleucine (HLNL) was isolated from bovine skin in high purity using two sequential purification steps. These consisted of preparative fibrous cellulose and size exclusion chromatography. The purified crosslink was then analysed using tandem mass spectrometry and high-resolution nuclear magnetic resonance (NMR) spectroscopy. The mass of singly and doubly charged ions of HLNL was 292.1865 and 146.5970 m/z and their optimised fragmentation energy was 17 keV and 5 keV, respectively. The 13C NMR of HLNL showed a doubled-up peak at 67.84 and 67.91 ppm which corroborated a diastereomeric form of collagen immature crosslink HLNL and both are chiroptically indistinguishable. The chemical structure was fully resolved using 1H, 13C and DEPT-135 high-resolution NMR spectroscopy and compared with other previous studies. We also obtained for the first time the 2D NMR spectra COSY and HSQC of HLNL. We therefore suggested that collagen organization into specific fibrils' orientation may be affected by the different configuration of these diastereomers of HLNL.
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Affiliation(s)
- Rafea Naffa
- NZ Leather and Shoe Research Association (LASRA®), Palmerston North, New Zealand. .,Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
| | - Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Gillian Norris
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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11
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Filitcheva J, Edwards PJB, Norris GE, Filichev VV. α-2′-Deoxyguanosine can switch DNA G-quadruplex topologies from antiparallel to parallel. Org Biomol Chem 2019; 17:4031-4042. [DOI: 10.1039/c9ob00360f] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
α-2′-Deoxyguanosine (α-dG) converts antiparallel, dimeric G-quadruplex DNA into a parallel, tetramolecular complex.
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Affiliation(s)
- Jana Filitcheva
- School of Fundamental Sciences
- Massey University
- Palmerston North
- New Zealand
| | | | - Gillian E. Norris
- School of Fundamental Sciences
- Massey University
- Palmerston North
- New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery
| | - Vyacheslav V. Filichev
- School of Fundamental Sciences
- Massey University
- Palmerston North
- New Zealand
- Maurice Wilkins Centre for Molecular Biodiscovery
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12
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Matthews ZM, Collett MG, Marshall JC, Partridge AC, Derrick PJ, Edwards PJB. Effect of a one-off sporidesmin challenge on the milk production of dairy cows. N Z Vet J 2018; 66:261-266. [DOI: 10.1080/00480169.2018.1492985] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Affiliation(s)
- ZM Matthews
- School of Veterinary Science, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
| | - MG Collett
- School of Veterinary Science, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
| | - JC Marshall
- School of Veterinary Science, Massey University, Private Bag 11222, Palmerston North 4442, New Zealand
| | - AC Partridge
- Chemical and Materials Engineering Department, University of Auckland, Auckland, New Zealand
| | - PJ Derrick
- Department of Physics, University of Auckland, Auckland, New Zealand; Deceased
| | - PJB Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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13
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Cameron AJ, Varnava KG, Edwards PJB, Harjes E, Sarojini V. Acyclic peptides incorporating the d-Phe-2-Abz turn motif: Investigations on antimicrobial activity and propensity to adopt β-hairpin conformations. J Pept Sci 2018; 24:e3094. [PMID: 29900628 DOI: 10.1002/psc.3094] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Revised: 05/08/2018] [Accepted: 05/16/2018] [Indexed: 02/01/2023]
Abstract
Three linear peptides incorporating d-Phe-2-Abz as the turn motif are reported. Peptide 1, a hydrophobic β-hairpin, served as a proof of principle for the design strategy with both NMR and CD spectra strongly suggesting a β-hairpin conformation. Peptides 2 and 3, designed as amphipathic antimicrobials, exhibited broad spectrum antimicrobial activity, with potency in the nanomolar range against Staphylococcus aureus. Both compounds possess a high degree of selectivity, proving non-haemolytic at concentrations 500 to 800 times higher than their respective minimal inhibitory concentrations (MICs) against S. aureus. Peptide 2 induced cell membrane and cell wall disintegration in both S. aureus and Pseudomonas aeruginosa as observed by transmission electron microscopy. Peptide 2 also demonstrated moderate antifungal activity against Candida albicans with an MIC of 50 μM. Synergism was observed with sub-MIC levels of amphotericin B (AmB), leading to nanomolar MICs against C. albicans for peptide 2. Based on circular dichroism spectra, both peptides 2 and 3 appear to exist as a mixture of conformers with the β-hairpin as a minor conformer in aqueous solution, and a slight increase in hairpin population in 50% trifluoroethanol, which was more pronounced for peptide 3. NMR spectra of peptide 2 in a 1:1 CD3 CN/H2 O mixture and 30 mM deuterated sodium dodecyl sulfate showed evidence of an extended backbone conformation of the β-strand residues. However, inter-strand rotating frame Overhauser effects (ROE) could not be detected and a loosely defined divergent hairpin structure resulted from ROE structure calculation in CD3 CN/H2 O. The loosely defined hairpin conformation is most likely a result of the electrostatic repulsions between cationic strand residues which also probably contribute towards maintaining low haemolytic activity.
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Affiliation(s)
- Alan J Cameron
- School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand
| | - Kyriakos G Varnava
- School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand
| | - Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4442, New Zealand
| | - Elena Harjes
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4442, New Zealand
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14
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Lepper CP, Williams MAK, Penny D, Edwards PJB, Jameson GB. Effects of Pressure and pH on the Hydrolysis of Cytosine: Implications for Nucleotide Stability around Deep-Sea Black Smokers. Chembiochem 2018; 19:540-544. [PMID: 29205716 DOI: 10.1002/cbic.201700555] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2017] [Indexed: 12/26/2022]
Abstract
The relatively low chemical stability of cytosine compared with other nucleobases is a key concern in origin-of-life scenarios, but the effect of pressure on the rate of hydrolysis of cytosine to uracil remains unknown. Through in situ NMR spectroscopy measurements, it has been determined that the half-life of cytosine at 373.15 K decreases from (18.0±0.7) days at ambient pressure (0.1 MPa) to (8.64±0.18) days at high pressure (200 MPa). This yields an activation volume for hydrolysis of (-11.8±0.5) cm3 mol-1 ; a decrease that is similar to the molar volume of water (18.0 cm3 mol-1 ) and consistent with a tetrahedral 3,3-hydroxyamine transition-state/intermediate species. Similar behaviour was also observed for cytidine. At both ambient and high pressures, the half-life of cytosine decreases significantly as the pH decreases from 7.0 to 6.0. These results provide scant support for the notion that RNA-based life forms originated in high-temperature, high-pressure, acidic environments.
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Affiliation(s)
- Christopher P Lepper
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand
| | - Martin A K Williams
- Institute of Fundamental Sciences, The MacDiarmid Institute and the Riddet Institute, Massey University, Palmerston North, Manawatu, 4442, New Zealand
| | - David Penny
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand
| | - Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4410, New Zealand
| | - Geoffrey B Jameson
- Institute of Fundamental Sciences, The MacDiarmid Institute and the Riddet Institute, Massey University, Palmerston North, Manawatu, 4442, New Zealand
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15
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Matthews ZM, Edwards PJB, Kahnt A, Collett MG, Marshall JC, Partridge AC, Harrison SJ, Fraser K, Cao M, Derrick PJ. Serum metabolomics using ultra performance liquid chromatography coupled to mass spectrometry in lactating dairy cows following a single dose of sporidesmin. Metabolomics 2018; 14:61. [PMID: 29706850 PMCID: PMC5904237 DOI: 10.1007/s11306-018-1358-4] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2017] [Accepted: 03/29/2018] [Indexed: 11/18/2022]
Abstract
INTRODUCTION Photosensitization is a common clinical sign in cows suffering from liver damage caused by the mycotoxin sporidesmin. This disease, called facial eczema (FE), is of major importance in New Zealand. Current techniques for diagnosing animals with subclinical sporidesmin-induced liver damage (i.e. without photosensitization) are nonspecific. In addition, little is known of the mechanisms involved in sporidesmin resistance, nor the early effects seen following low-dose sporidesmin intoxication. OBJECTIVE The objective of this study was to identify individual metabolites or metabolic profiles that could be used as serum markers for early stage FE in lactating cows. METHODS Results are presented from a 59-day sporidesmin challenge in Friesian-cross dairy cows. Serum metabolite profiles were obtained using reversed phase ultra-performance liquid chromatography (UPLC) electrospray ionization mass spectrometry (MS) and UPLC tandem MS. Multivariate and time series analyses were used to assess the data. RESULTS Statistical analysis, both with and without the temporal component, could distinguish the profiles of animals with clinical signs from the others, but not those affected subclinically. An increase in the concentrations of a combination of taurine- and glycine-conjugated secondary bile acids (BAs) was the most likely cause of the separation. This is the first time that MS methods have been applied to FE and that bile acids changes have been detected in cattle exposed to sporidesmin. CONCLUSIONS It is well known that BA concentrations increase during cholestasis due to damage to bile ducts and leakage of the bile. This is the first study to investigate metabolomic changes in serum following a sporidesmin challenge. Further work to establish the significance of the elevation of individual BAs concentrations in the serum of early-stage sporidesmin-poisoned cows is necessary.
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Affiliation(s)
| | | | | | | | | | | | | | - Karl Fraser
- AgResearch Grasslands, Palmerston North, New Zealand
| | - Mingshu Cao
- AgResearch Grasslands, Palmerston North, New Zealand
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16
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Cameron AJ, Edwards PJB, Harjes E, Sarojini V. Tyrocidine A Analogues Bearing the Planar d-Phe-2-Abz Turn Motif: How Conformation Impacts Bioactivity. J Med Chem 2017; 60:9565-9574. [DOI: 10.1021/acs.jmedchem.7b00953] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Affiliation(s)
- Alan J. Cameron
- School
of Chemical Sciences, University of Auckland, Auckland 1142, New Zealand
| | - Patrick J. B. Edwards
- Institute
of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Elena Harjes
- Institute
of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
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17
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Cameron AJ, Squire CJ, Edwards PJB, Harjes E, Sarojini V. Crystal and NMR Structures of a Peptidomimetic β-Turn That Provides Facile Synthesis of 13-Membered Cyclic Tetrapeptides. Chem Asian J 2017; 12:3195-3202. [PMID: 29098772 DOI: 10.1002/asia.201701422] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Revised: 10/30/2017] [Indexed: 12/31/2022]
Abstract
Herein we report the unique conformations adopted by linear and cyclic tetrapeptides (CTPs) containing 2-aminobenzoic acid (2-Abz) in solution and as single crystals. The crystal structure of the linear tetrapeptide H2 N-d-Leu-d-Phe-2-Abz-d-Ala-COOH (1) reveals a novel planar peptidomimetic β-turn stabilized by three hydrogen bonds and is in agreement with its NMR structure in solution. While CTPs are often synthetically inaccessible or cyclize in poor yield, both 1 and its N-Me-d-Phe analogue (2) adopt pseudo-cyclic frameworks enabling near quantitative conversion to the corresponding CTPs 3 and 4. The crystal structure of the N-methylated peptide (4) is the first reported for a CTP containing 2-Abz and reveals a distinctly planar 13-membered ring, which is also evident in solution. The N-methylation of d-Phe results in a peptide bond inversion compared to the conformation of 3 in solution.
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Affiliation(s)
- Alan J Cameron
- School of Chemical Sciences, The University of Auckland, Auckland, 1142, New Zealand
| | - Christopher J Squire
- School of Biological Sciences, The University of Auckland, Auckland, 1142, New Zealand
| | - Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4442, New Zealand
| | - Elena Harjes
- Institute of Fundamental Sciences, Massey University, Palmerston North, 4442, New Zealand
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18
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Mittal VA, Ellis A, Ye A, Edwards PJB, Singh H. The adsorption of orthophosphate onto casein-iron precipitates. Food Chem 2017; 239:17-22. [PMID: 28873555 DOI: 10.1016/j.foodchem.2017.06.035] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Revised: 06/01/2017] [Accepted: 06/06/2017] [Indexed: 10/19/2022]
Abstract
This study explored the interactions of orthophosphate with casein-iron precipitates. Casein-iron precipitates were formed by adding ferric chloride at ≥10mM to sodium caseinate solutions ranging in concentration from 1 to 3%(w/v). The addition of different concentrations of orthophosphate solution to the casein-iron precipitates resulted in gradual adsorption of the orthophosphate, causing re-dispersion of the casein-iron complexes. The interactions of added orthophosphate with iron in the presence and absence of caseins are postulated, and new mechanisms are proposed. The re-dispersed soluble complexes of casein-iron-orthophosphate generated using this process could be used as novel iron fortificants.
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Affiliation(s)
- Vikas A Mittal
- Riddet Institute, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand.
| | - Ashling Ellis
- Riddet Institute, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand; Massey Institute of Food Science and Technology, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand.
| | - Aiqian Ye
- Riddet Institute, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand; Massey Institute of Food Science and Technology, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand.
| | - Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand.
| | - Harjinder Singh
- Riddet Institute, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand; Massey Institute of Food Science and Technology, Massey University, Private Bag 11 222, Palmerston North 4474, New Zealand.
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19
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Doluca O, Withers JM, Loo TS, Edwards PJB, González C, Filichev VV. Interdependence of pyrene interactions and tetramolecular G4-DNA assembly. Org Biomol Chem 2015; 13:3742-8. [DOI: 10.1039/c4ob02499k] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Our results demonstrate the expanded capabilities of G-quadruplex DNAs for directed chromophore arrangements and show new perspectives in the design of G-quadruplexes governed by non-guanine moieties.
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Affiliation(s)
- Osman Doluca
- College of Sciences
- Institute of Fundamental Sciences
- Massey University
- 4442 Palmerston North
- New Zealand
| | - Jamie M. Withers
- College of Sciences
- Institute of Fundamental Sciences
- Massey University
- 4442 Palmerston North
- New Zealand
| | - Trevor S. Loo
- College of Sciences
- Institute of Fundamental Sciences
- Massey University
- 4442 Palmerston North
- New Zealand
| | - Patrick J. B. Edwards
- College of Sciences
- Institute of Fundamental Sciences
- Massey University
- 4442 Palmerston North
- New Zealand
| | | | - Vyacheslav V. Filichev
- College of Sciences
- Institute of Fundamental Sciences
- Massey University
- 4442 Palmerston North
- New Zealand
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20
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Suzuki R, Irie R, Harntaweesup Y, Tachibana K, Holland PT, Harwood DT, Shi F, Beuzenberg V, Itoh Y, Pascal S, Edwards PJB, Satake M. Brevisulcatic acids, marine ladder-frame polyethers from the red tide dinoflagellate Karenia brevisulcata in New Zealand. Org Lett 2014; 16:5850-3. [PMID: 25356530 DOI: 10.1021/ol502700h] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The isolation and structural determination of new marine ladder-frame polyethers, brevisulcatic acids-1 (1) and -4 (2) are reported. Brevisulcatic acids were isolated from the dinoflagellate Karenia brevisulcata, which was identified as the causative species of a major red tide event in New Zealand in 1998. The ether ring composition and a β-hydroxy, γ-methylene valeric acid side chain of 1 and 2 are common, but 2 has a γ-lactone as the 5-membered A-ring while 1 is the seco acid analogue. Compound 2 has structural and bioactivity similarities to brevetoxin A.
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Affiliation(s)
- Rina Suzuki
- Department of Chemistry, School of Science, The University of Tokyo , 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan
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21
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Doluca O, Hale TK, Edwards PJB, González C, Filichev VV. Assembly Dependent Fluorescence Enhancing Nucleic Acids in Sequence-Specific Detection of Double-Stranded DNA. Chempluschem 2014; 79:2. [PMID: 31986772 DOI: 10.1002/cplu.201300369] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Invited for this month's cover is the group of Dr. Vyacheslav V. Filichev from Massey University, New Zealand and a collaborator from the Instituto de Química Física Rocasalano, CSIC, Spain. The cover picture shows how a DNA strand that forms a highly stable G-quadruplex can be converted into an efficient DNA triplex-forming oligonucleotide by incorporating a pyrene intercalator into the sequence. Read the full text of the article at 10.1002/cplu.201300310.
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Affiliation(s)
- Osman Doluca
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682.,International Burch University, Francuske Revolucije, 71210 Sarajevo (Bosnia and Herzegovina)
| | - Tracy K Hale
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682
| | - Patrick J B Edwards
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682
| | - Carlos González
- Instituto de Química Física Rocasalano, CSIC, Serrano 119, 28006 Madrid (Spain)
| | - Vyacheslav V Filichev
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682
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22
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Doluca O, Hale TK, Edwards PJB, González C, Filichev VV. Assembly Dependent Fluorescence Enhancing Nucleic Acids in Sequence-Specific Detection of Double-Stranded DNA. Chempluschem 2013; 79:58-66. [PMID: 31986766 DOI: 10.1002/cplu.201300310] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2013] [Revised: 10/29/2013] [Indexed: 12/19/2022]
Abstract
In this study the position of the thiazole orange derivative in triplex-forming oligonucleotides (TFOs) is varied and the fluorescence of the resulting complexes with DNA duplexes, single-stranded DNAs and RNAs are evaluated. Under similar conditions single attachment of the TO-dye to 2'-O-propargyl nucleotides in the TFOs (assembly dependent fluorescence enhancing nucleic acids, AFENA) led to probes with low fluorescent intensity in the single-stranded state with fluorescence quantum yield (ΦF ) of 0.9 %-1.5 %. Significant increase in fluorescence intensity was detected after formation of DNA triplexes (ΦF =23.5 %-34.9 %). Under similar conditions, Watson-Crick-type duplexes formed by the probes with single stranded (ss) RNA and ssDNA showed lower fluorescence intensities. Bugle insertions of twisted intercalating nucleic acid (TINA) monomers were shown to improve the fluorescent characteristics of GT/GA-containing antiparallel AFENA-TFOs. Self-aggregation of TFOs caused by guanosines was eliminated by TINA insertion which also promoted DNA triplex formation at pH 7.2. Importantly these AFENA-TINA-TFOs can bind to the duplex in the presence of complementary RNA at 37 °C.
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Affiliation(s)
- Osman Doluca
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682.,International Burch University, Francuske Revolucije, 71210 Sarajevo (Bosnia and Herzegovina)
| | - Tracy K Hale
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682
| | - Patrick J B Edwards
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682
| | - Carlos González
- Instituto de Química Física Rocasalano, CSIC, Serrano 119, 28006 Madrid (Spain)
| | - Vyacheslav V Filichev
- College of Sciences, Institute of Fundamental Sciences, Massey University, Private Bag 11-222, 4442 Palmerston North (New Zealand), Fax: (+64) 6-3505682
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23
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Doluca O, Hale TK, Edwards PJB, González C, Filichev VV. Cover Picture: Assembly Dependent Fluorescence Enhancing Nucleic Acids in Sequence-Specific Detection of Double-Stranded DNA (ChemPlusChem 1/2014). Chempluschem 2013. [DOI: 10.1002/cplu.201300370] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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24
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Ainscough EW, Brodie AM, Edwards PJB, Jameson GB, Otter CA, Kirk S. Zinc, Cadmium, and Mercury Complexes of a Pyridyloxy-Substituted Cyclotriphosphazene: Syntheses, Structures, and Fluxional Behavior. Inorg Chem 2012; 51:10884-92. [DOI: 10.1021/ic3013574] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Eric W. Ainscough
- Chemistry—Institute
of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand 4442
| | - Andrew M. Brodie
- Chemistry—Institute
of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand 4442
| | - Patrick J. B. Edwards
- Chemistry—Institute
of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand 4442
| | - Geoffrey B. Jameson
- Chemistry—Institute
of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand 4442
| | - Carl A. Otter
- Chemistry—Institute
of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand 4442
| | - Stephen Kirk
- Chemistry—Institute
of Fundamental
Sciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand 4442
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25
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Venugopal H, Edwards PJB, Schwalbe M, Claridge JK, Libich DS, Stepper J, Loo T, Patchett ML, Norris GE, Pascal SM. Structural, Dynamic, and Chemical Characterization of a Novel S-Glycosylated Bacteriocin. Biochemistry 2011; 50:2748-55. [DOI: 10.1021/bi200217u] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Hariprasad Venugopal
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | | | - Martin Schwalbe
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Jolyon K. Claridge
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - David S. Libich
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
| | - Judith Stepper
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand
| | - Trevor Loo
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand
| | - Mark L. Patchett
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand
| | - Gillian E. Norris
- Institute of Molecular Biosciences, Massey University, Palmerston North, New Zealand
| | - Steven M. Pascal
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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26
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Hentschke R, Edwards PJB, Boden N, Bushby RJ. A model for isotropic, nematic, and columnar ordering in a self-assembling system - comparison with the phase behavior of 2,3,6,7,10,11-hexa-(1,4,7-trioxaoctyl)-triphenylene in water. ACTA ACUST UNITED AC 2011. [DOI: 10.1002/masy.19940810137] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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27
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Schwalbe M, Dutta K, Libich DS, Venugopal H, Claridge JK, Gell DA, Mackay JP, Edwards PJB, Pascal SM. Two-state conformational equilibrium in the Par-4 leucine zipper domain. Proteins 2010; 78:2433-49. [PMID: 20602362 DOI: 10.1002/prot.22752] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Prostate apoptosis response factor-4 (Par-4) is a pro-apoptotic and tumor-suppressive protein. A highly conserved heptad repeat sequence at the Par-4 C-terminus suggests the presence of a leucine zipper (LZ). This C-terminal region is essential for Par-4 self-association and interaction with various effector proteins. We have used nuclear magnetic resonance (NMR) spectroscopy to fully assign the chemical shift resonances of a peptide comprising the LZ domain of Par-4 at neutral pH. Further, we have investigated the properties of the Par-4 LZ domain and two point mutants under a variety of conditions using NMR, circular dichroism (CD), light scattering, and bioinformatics. Results indicate an environment-dependent conformational equilibrium between a partially ordered monomer (POM) and a predominantly coiled coil dimer (CCD). The combination of techniques used allows the time scales of the equilibrium to be probed and also helps to identify features of the amino acid sequence that may influence the equilibrium.
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Affiliation(s)
- Martin Schwalbe
- Centre for Structural Biology, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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28
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Lepper C, Edwards PJB, Schuster E, Brown JR, Dykstra R, Callaghan PT, Williams MAK. Rheo-NMR studies of the behavior of a nematic liquid crystal in a low-shear-rate regime: the transition from director alignment to reorientation. Phys Rev E Stat Nonlin Soft Matter Phys 2010; 82:041712. [PMID: 21230300 DOI: 10.1103/physreve.82.041712] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/12/2010] [Indexed: 05/30/2023]
Abstract
Deuterium NMR spectroscopy has been used to study the director dynamics of the nematic liquid-crystal system cetyl trimethylammonium bromide/D2O under the action of applied viscous torques. Shear forces were applied using a custom-built Couette cell that was introduced into an NMR superconducting magnet, so that its rotational axis was parallel to the magnetic field direction, along which the liquid-crystal director originally aligned. Subsequently, the inner cylinder of the cell was rotated continuously at different rates using a stepper motor. The resulting time evolution and ultimate steady-state orientation of the director, governed by the competition between the applied viscous torque with elastic and magnetic terms, was measured via observed changes in the deuterium spectrum. Using a simple gearbox allowed unprecedented access to a low-shear-rate regime in which, above a threshold shear rate, the director of part of the sample was observed to reorient, while the remaining part still aligned with the magnetic field. Subsequent increases in the applied rotational rate were found to increase the relative proportion of the orienting fraction. Spatially resolved NMR spectra showed that the orienting and field-aligned fractions formed separated bands across the gap of the Couette cell, with director reorientation being initiated at the moving inner wall. The behavior was found to be consistent with the often ignored variation in velocity gradient manifest across the gap of a cylindrical cell, so that as the angular frequency of the inner cylinder was increased the radial location of the critical shear rate required for reorientation traversed the gap. Once the applied rotational rate was sufficient to reorient the director of the entire sample, the dependence of the exhibited steady-state orientation on the average applied shear rate was measured. These results could be fitted to an analytical solution of the force-balance equation, made tractable by the assumption that the elasticity term was of minor significance and could be ignored. Additionally, the use of a numerical solution of the full force-balance equation, which explicitly includes elasticity and secondary flow and additionally allows the time evolution of the director orientation to be calculated, was investigated.
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Affiliation(s)
- C Lepper
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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Edwards PJB, Kakubayashi M, Dykstra R, Pascal SM, Williams MAK. Rheo-NMR studies of an enzymatic reaction: evidence of a shear-stable macromolecular system. Biophys J 2010; 98:1986-94. [PMID: 20441763 DOI: 10.1016/j.bpj.2010.01.022] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2009] [Revised: 01/07/2010] [Accepted: 01/11/2010] [Indexed: 12/16/2022] Open
Abstract
Understanding the effects of shear forces on biopolymers is key to understanding how biological systems function. Although currently there is good agreement between theoretical predictions and experimental measurements of the behavior of DNA and large multimeric proteins under shear flow, applying the same arguments to globular proteins leads to the prediction that they should only exhibit shear-induced conformational changes at extremely large shear rates. Nevertheless, contradictory experimental evidence continues to appear, and the effect of shear on these biopolymers remains contentious. Here, a custom-built rheo-NMR cell was used to investigate whether shear flow modifies enzyme action compared with that observed quiescently. Specifically, (1)H NMR was used to follow the kinetics of the liberation of methanol from the methylesterified polysaccharide pectin by pectinmethylesterase enzymes. Two different demethylesterifying enzymes, known to have different action patterns, were used. In all experiments performed, Couette flows with shear rates of up to 1570 s(-1) did not generate detectable differences in the rate of methanol liberation compared to unsheared samples. This study provides evidence for a shear-stable macromolecular system consisting of a largely beta-sheet protein and a polysaccharide, in line with current theoretical predictions, but in contrast to some other experimental work on other proteins.
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Affiliation(s)
- Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand
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30
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Headey SJ, MacAskill UK, Wright MA, Claridge JK, Edwards PJB, Farley PC, Christeller JT, Laing WA, Pascal SM. Solution structure of the squash aspartic acid proteinase inhibitor (SQAPI) and mutational analysis of pepsin inhibition. J Biol Chem 2010; 285:27019-27025. [PMID: 20538608 DOI: 10.1074/jbc.m110.137018] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The squash aspartic acid proteinase inhibitor (SQAPI), a proteinaceous proteinase inhibitor from squash, is an effective inhibitor of a range of aspartic proteinases. Proteinaceous aspartic proteinase inhibitors are rare in nature. The only other example in plants probably evolved from a precursor serine proteinase inhibitor. Earlier work based on sequence homology modeling suggested SQAPI evolved from an ancestral cystatin. In this work, we determined the solution structure of SQAPI using NMR and show that SQAPI shares the same fold as a plant cystatin. The structure is characterized by a four-strand anti-parallel beta-sheet gripping an alpha-helix in an analogous manner to fingers of a hand gripping a tennis racquet. Truncation and site-specific mutagenesis revealed that the unstructured N terminus and the loop connecting beta-strands 1 and 2 are important for pepsin inhibition, but the loop connecting strands 3 and 4 is not. Using ambiguous restraints based on the mutagenesis results, SQAPI was then docked computationally to pepsin. The resulting model places the N-terminal strand of SQAPI in the S' side of the substrate binding cleft, whereas the first SQAPI loop binds on the S side of the cleft. The backbone of SQAPI does not interact with the pepsin catalytic Asp(32)-Asp(215) diad, thus avoiding cleavage. The data show that SQAPI does share homologous structural elements with cystatin and appears to retain a similar protease inhibitory mechanism despite its different target. This strongly supports our hypothesis that SQAPI evolved from an ancestral cystatin.
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Affiliation(s)
- Stephen J Headey
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Ursula K MacAskill
- Institute of Molecular Biosciences, Massey University, Palmerston North 4442, New Zealand
| | - Michele A Wright
- The New Zealand Institute for Plant & Food Research Limited, Auckland 1142, New Zealand
| | - Jolyon K Claridge
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Patrick J B Edwards
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand
| | - Peter C Farley
- Institute of Molecular Biosciences, Massey University, Palmerston North 4442, New Zealand
| | - John T Christeller
- The New Zealand Institute for Plant & Food Research Limited, Palmerston North 4442, New Zealand
| | - William A Laing
- The New Zealand Institute for Plant & Food Research Limited, Auckland 1142, New Zealand.
| | - Steven M Pascal
- Institute of Fundamental Sciences, Massey University, Palmerston North 4442, New Zealand.
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31
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Sun X, Jones WT, Harvey D, Edwards PJB, Pascal SM, Kirk C, Considine T, Sheerin DJ, Rakonjac J, Oldfield CJ, Xue B, Dunker AK, Uversky VN. N-terminal domains of DELLA proteins are intrinsically unstructured in the absence of interaction with GID1/gibberellic acid receptors. J Biol Chem 2010; 285:11557-71. [PMID: 20103592 PMCID: PMC2857034 DOI: 10.1074/jbc.m109.027011] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 01/07/2010] [Indexed: 11/06/2022] Open
Abstract
The plant growth-repressing DELLA proteins (DELLAs) are known to represent a convergence point in integration of multiple developmental and environmental signals in planta, one of which is hormone gibberellic acid (GA). Binding of the liganded GA receptor (GID1/GA) to the N-terminal domain of DELLAs is required for GA-induced degradation of DELLAs via the ubiquitin-proteasome pathway, thus derepressing plant growth. However, the conformational changes of DELLAs upon binding to GID1/GA, which are the key to understanding the precise mechanism of GID1/GA-mediated degradation of DELLAs, remain unclear. Using biophysical, biochemical, and bioinformatics approaches, we demonstrated for the first time that the unbound N-terminal domains of DELLAs are intrinsically unstructured proteins under physiological conditions. Within the intrinsically disordered N-terminal domain of DELLAs, we have identified several molecular recognition features, sequences known to undergo disorder-to-order transitions upon binding to interacting proteins in intrinsically unstructured proteins. In accordance with the molecular recognition feature analyses, we have observed the binding-induced folding of N-terminal domains of DELLAs upon interaction with AtGID1/GA. Our results also indicate that DELLA proteins can be divided into two subgroups in terms of their molecular compactness and their interactions with monoclonal antibodies.
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Affiliation(s)
- Xiaolin Sun
- From the New Zealand Institute for Plant and Food Research, Private Bag 11 030, Palmerston North, New Zealand
| | - William T. Jones
- From the New Zealand Institute for Plant and Food Research, Private Bag 11 030, Palmerston North, New Zealand
| | - Dawn Harvey
- From the New Zealand Institute for Plant and Food Research, Private Bag 11 030, Palmerston North, New Zealand
| | | | - Steven M. Pascal
- the Centre for Structural Biology, Institute of Fundamental Sciences, and
| | - Christopher Kirk
- From the New Zealand Institute for Plant and Food Research, Private Bag 11 030, Palmerston North, New Zealand
- the Institute of Molecular Biosciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand
| | - Thérèse Considine
- the Fonterra Research Centre, Private Bag 11 029, Palmerston North, New Zealand
| | - David J. Sheerin
- the Institute of Molecular Biosciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand
| | - Jasna Rakonjac
- the Institute of Molecular Biosciences, Massey University, Private Bag 11 222, Palmerston North, New Zealand
| | - Christopher J. Oldfield
- the Center for Computational Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, School of Medicine, Indiana University, Indianapolis, Indiana 46202, and
| | - Bin Xue
- the Center for Computational Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, School of Medicine, Indiana University, Indianapolis, Indiana 46202, and
| | - A. Keith Dunker
- the Center for Computational Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, School of Medicine, Indiana University, Indianapolis, Indiana 46202, and
| | - Vladimir N. Uversky
- the Center for Computational Biology and Bioinformatics, Department of Biochemistry and Molecular Biology, School of Medicine, Indiana University, Indianapolis, Indiana 46202, and
- the Institute for Biological Instrumentation, Russian Academy of Sciences, 142290 Pushchino, Moscow Region, Russia
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Ponniah K, Loo TS, Edwards PJB, Pascal SM, Jameson GB, Norris GE. The production of soluble and correctly folded recombinant bovine beta-lactoglobulin variants A and B in Escherichia coli for NMR studies. Protein Expr Purif 2009; 70:283-9. [PMID: 20018245 DOI: 10.1016/j.pep.2009.12.006] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2009] [Revised: 12/04/2009] [Accepted: 12/09/2009] [Indexed: 10/20/2022]
Abstract
The production of soluble and correctly folded eukaryotic proteins in prokaryotic systems has always been hampered by the difference in or lack of cell machinery responsible for folding, post-translation modification and secretion of the proteins involved. In the case of bovine beta-lactoglobulin (BLG), a major cow's milk allergen and a protein widely used for protein folding studies, a eukaryotic yeast expression system has been the preferred choice of many researchers, particularly for the production of isotopically labeled protein required for NMR studies. Although this system yields high amounts of recombinant protein, the BLG produced is usually associated with extracellular polysaccharides, which is problematic for NMR analysis. In our study we show that when co-expressed with the signal-sequence-less disulfide bond isomerase (Delta ssDsbC) in the dual expression vector, pETDUET-1, both BLG A and BLG B can be reproducibly produced in a soluble form. Expression was carried out in Escherichia coli Origami(DE3), a trxB/gor mutant for thioredoxin- and glutathione reductase, which allows for proper formation of disulfide bonds in the cytoplasm. The protein was purified by anion exchange chromatography followed by salting-out at low pH and size exclusion chromatography. Our expression system is able to consistently produce milligram quantities of correctly folded BLG A and B with no additional amino acid residues at the N-terminus, except for a methionine. (15)N-labeled BLG A and B, prepared and purified using this method, produced HSQC spectra typical of native bovine BLG.
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Affiliation(s)
- Komala Ponniah
- Institute of Molecular BioSciences, Massey University, Private Bag 11222, Palmerston North, New Zealand
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Libich DS, Schwalbe M, Kate S, Venugopal H, Claridge JK, Edwards PJB, Dutta K, Pascal SM. Intrinsic disorder and coiled-coil formation in prostate apoptosis response factor 4. FEBS J 2009; 276:3710-28. [PMID: 19490121 DOI: 10.1111/j.1742-4658.2009.07087.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Prostate apoptosis response factor-4 (Par-4) is an ubiquitously expressed pro-apoptotic and tumour suppressive protein that can both activate cell-death mechanisms and inhibit pro-survival factors. Par-4 contains a highly conserved coiled-coil region that serves as the primary recognition domain for a large number of binding partners. Par-4 is also tightly regulated by the aforementioned binding partners and by post-translational modifications. Biophysical data obtained in the present study indicate that Par-4 primarily comprises an intrinsically disordered protein. Bioinformatic analysis of the highly conserved Par-4 reveals low sequence complexity and enrichment in polar and charged amino acids. The high proteolytic susceptibility and an increased hydrodynamic radius are consistent with a largely extended structure in solution. Spectroscopic measurements using CD and NMR also reveal characteristic features of intrinsic disorder. Under physiological conditions, the data obtained show that Par-4 self-associates via the C-terminal domain, forming a coiled-coil. Interruption of self-association by urea also resulted in loss of secondary structure. These results are consistent with the stabilization of the coiled-coil motif through an intramolecular association.
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Affiliation(s)
- David S Libich
- Centre for Structural Biology, Institute of Fundamental Sciences, Massey University, Palmerston North, New Zealand.
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Comeskey DJ, Montefiori M, Edwards PJB, McGhie TK. Isolation and structural identification of the anthocyanin components of red kiwifruit. J Agric Food Chem 2009; 57:2035-9. [PMID: 19203266 DOI: 10.1021/jf803287d] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The anthocyanins responsible for the red color of red kiwifruit were extracted in acidified ethanol and isolated by solid phase extraction (SPE) followed by preparative HPLC. Five anthocyanins were obtained and subsequently identified as delphinidin 3-[2-(xylosyl)galactoside], delphinidin 3-galactoside, cyanidin 3-[2-(xylosyl)galactoside], cyanidin 3-galactoside, and cyanidin 3-glucoside by a combination of LC-MS/MS, GC-MS, and 2D NMR. Delphinidin 3-[2-(xylosyl)galactoside] and delphinidin 3-galactoside have not previously been reported in the genus Actinidia.
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Affiliation(s)
- Daniel J Comeskey
- The New Zealand Institute for Plant and Food Research Ltd, Private Bag 11600, Palmerston North 4442, New Zealand
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35
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Koulman A, Seeliger C, Edwards PJB, Fraser K, Simpson W, Johnson L, Cao M, Rasmussen S, Lane GA. E/Z-Thesinine-O-4'-alpha-rhamnoside, pyrrolizidine conjugates produced by grasses (Poaceae). Phytochemistry 2008; 69:1927-32. [PMID: 18466931 DOI: 10.1016/j.phytochem.2008.03.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2007] [Revised: 03/17/2008] [Accepted: 03/20/2008] [Indexed: 05/13/2023]
Abstract
Based on direct infusion mass spectrometry we identified a novel alkaloid as a major component of perennial ryegrass (Lolium perenne). Initial mass spectral data suggested it to be a pyrrolizidine conjugate. As this class of alkaloids has not been described before from grasses, we isolated it to elucidate its structure. The isolated alkaloid proved to be a mixture of two stereoisomers. The structures of the two compounds as determined by 1D and 2D NMR spectroscopy, were E-thesinine-O-4'-alpha-rhamnoside (1) and Z-thesinine-O-4'-alpha-rhamnoside (2). These identifications were supported by the characterisation by GC-MS and optical rotation of (+)-isoretronecanol as the necine base released on alkaline hydrolysis of these alkaloids. 1 and 2 together with the aglycone and a hexoside were also detected in tall fescue (Festuca arundinacea). This is the first report of pyrrolizidine alkaloids produced by grasses (Poaceae).
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Affiliation(s)
- Albert Koulman
- AgResearch Grasslands Research Centre, Tennent Drive, Private Bag 11008, Palmerston North, New Zealand
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36
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Spencer P, Sivakumaran S, Fraser K, Foo LY, Lane GA, Edwards PJB, Meagher LP. Isolation and characterisation of procyanidins from Rumex obtusifolius. Phytochem Anal 2007; 18:193-203. [PMID: 17500361 DOI: 10.1002/pca.967] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
An acetone:water (7:3) extract obtained from the leaves of Rumex obtusifolius was fractionated into procyanidin oligomer and polymer fractions using a linear gradient and a simple step method on Sephadex LH-20. The chemical characteristics of the procyanidin fractions were studied by 13C-NMR spectroscopy, acid-catalysed degradation in the presence of benzyl mercaptan, matrix-assisted laser desorption/ionisation time-of-flight (MALDI-TOF) MS and electrospray ionisation (ESI) MS. The 13C-NMR showed that the polymer fraction consisted predominantly of procyanidin polymers, some with galloyl groups attached. The thiolysis reaction products indicated a mean degree of polymerisation (DP) of 4.3 for the step method, and a range of 2.3-8.2 mean DP for the gradient fractionation, with epicatechin as the most abundant flavan-3-ol extension unit, while the terminal units consisted of equal proportions of catechin, epicatechin and epicatechin gallate. Singly charged ions observed in MALDI-TOF/MS showed a range of oligomeric procyanidins and their polygalloyl derivatives. These species (in the range DP 2-7) were also observed by ESI/MS but the spectra were more complex due to overlapping multiply charged ions. Isolation of oligomers from the Sephadex LH-20 fraction by chromatography on polyamide and C18 yielded B1, B2, B3 and B7 dimers, an A-type trimer and a B2 3,3'-O-digallate.
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Affiliation(s)
- Paul Spencer
- Food and Health, AgResearch Ltd., Grasslands Research Centre, PB11008, Palmerston North, New Zealand
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37
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Abstract
[structure: see text] A series of eight dipeptides of the general formula Ac-Phe-Pro-NHMe was synthesized and the thermodynamics of the cis --> trans isomerization about the central amide bond were studied by NMR. Pro* represents the following prolines: l-proline (Pro), l-trans-4-hydroxyproline (Hyp), l-cis-4-hydroxyproline (hyp), l-cis-4-methoxyproline (hyp[OMe]), l-trans-3-hydroxyproline (3-Hyp), l-cis-3-hydroxyproline (3-hyp), l-2,3-trans-3,4-cis-3,4-dihydroxyproline (DHP), and l-2,3-cis-3,4-trans-3,4-dihydroxyproline (dhp). The conformation of the pyrrolidine ring in each case is discussed in light of previous structural studies, analysis of potential stereoelectronic effects, and NMR data. Hydroxy substituents at C-4 have a greater impact on cis --> trans isomerization than analogous substituents at C-3 as a result of the intervening bond distances and bridging groups. The position of the equilibrium and its dependence on temperature are a reflection of both enthalpic and entropic factors, the latter being complicated in this study by an Ar-Pro interaction in the cis conformation. The substituents on the pyrrolidine ring determine the conformation of the five-membered ring, which in turn influences the strength of the Ar-Pro interaction, backbone dihedral angles, and the relative energy of the cis and trans species. The ultimate position of the equilibrium depends on a complex blend of steric, electronic, and conformational factors.
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Affiliation(s)
- Carol M Taylor
- Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand.
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38
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Abstract
[reaction: see text] NMR was used to study the thermodynamics of the cis --> trans isomerization for prolyl amide bonds in the compounds shown. The magnitude of K(t/c) for C-terminal esters is greater than for the corresponding amides, signifying stronger backbone stereoelectronic effects in esters. Increasing the steric bulk of the N-terminal residue from Ac- to Ac-Gly- favors the trans conformation. Incorporation of a Phe residue N-terminal to Pro, however, shifts the equilibrium in favor of the cis conformation, via a stabilizing aromatic-proline interaction.
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Affiliation(s)
- Carol M Taylor
- Institute of Fundamental Sciences, Massey University, Private Bag 11-222, Palmerston North, New Zealand.
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Smith MH, Edwards PJB, Palmano KP, Creamer LK. Structural features of bovine caseinomacropeptide A and B by 1H nuclear magnetic resonance spectroscopy. J DAIRY RES 2002; 69:85-94. [PMID: 12047114 DOI: 10.1017/s0022029901005271] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Samples of bovine caseinomacropeptide (CMP) were isolated from kappa-casein A and kappa-casein B and fractionated to give aglycosylated CMP A and CMP B and monoglycosylated CMP A. The secondary structures of these three peptides were compared under neutral and acidic (pH 4.2) conditions, using two-dimensional (2D) 1H nuclear magnetic resonance (NMR) spectroscopy. The differences between the spectra at pH 4.2 and 7.0 and the spectra of the aglycosylated and glycosylated CMP A were subtle, indicating little change in backbone conformation with these changes. These results Suggest that differences in the coagulation properties of milks containing either kappa-casein A or kappa-casein B are more likely to be related to factors, such as micelle size or charge, than to structural differences arising from altered backbone conformation of the macropeptide segments of the kappa-caseins.
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Affiliation(s)
- Mark H Smith
- Food Science Section, New Zealand Dairy Research Institute, Palmerston North, New Zealand
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