A chemical study of yoghurt produced under isostatic pressure during storage

Yoghurt fermented under sub-lethal high pressure (10, 20, 30 and 40 MPa at 43 °C), and afterward placed under refrigeration (4 °C for 23 days) was studied and compared with yoghurt fermented at atmospheric pressure (0.1 MPa). For a deeper analysis, metabolite fingerprinting by nuclear magnetic resonance (NMR), sugars and organic acids assessment by high performance liquid chromatography (HPLC), total fatty acids (TFA) determination and quantification by gas chromatography with a flame ionization detector (GC-FID) were performed. Metabolomic analyses revealed that only 2,3-butanediol, acetoin, diacetyl and formate vary with the increase of pressure and probable relation with pressure influenced diacetyl reductase, acetoin reductase and acetolactate decarboxylase. Yoghurts fermented at 40 MPa had the lowest content in lactose (39.7 % of total sugar reduction) and the less content in TFA (56.1 %). Further research is of interest to understand more about fermentation processes under sub-lethal high pressure.

Aging and Proteins: What Does Proteostasis Have to Do with Age?

The world is aging and we must face the challenges that this brings. One of the reasons for the increasing aging of the world's population is the increase in life expectancy and, since we live longer, it is of paramount importance to live well and to prevent age-associated diseases. In this way, it is crucial to improve knowledge of the aging process and of the mechanisms that contribute to it. Ideally it would be of great interest to have a panel of biomarkers of healthy aging that would allow an estimate of the biological age of an individual. One of the changes that greatly contribute to aging is the loss of protein homeostasis, also called proteostasis. To ensure the proper function of cells and to maintain cellular proteostasis, organisms have developed systems to control protein synthesis, folding and degradation. Loss or dysfunction of proteostasis is at the root of many well-studied human neurological diseases, such as Alzheimer's disease and, more recently, it has been implicated in the aging process with some reports showing long-lived animals to have improved proteostasis. Growing evidence suggests a strong link between modifications in the quantity and/or activity of several players involved in proteostasis and longevity. In this review, we give an overview of the main characteristics of aging with focus on proteostasis. We present how changes in components of proteostasis, during aging, impact the lifespan of model organisms. We also briefly review the current state of aging biomarkers and discuss the potential of proteostasis network components as markers of healthy aging.

Host-defense peptides AC12, DK16 and RC11 with immunomodulatory activity isolated from Hypsiboas raniceps skin secretion

Inflammation is a natural defense mechanism of the immune system; however, when unregulated, it can lead to chronic illness. Glucocorticoids are the most commonly used agents to effectively treat inflammatory conditions, including autoimmune diseases, however these substances can trigger a number of side effects. Thus, viable alternatives to the use of these drugs would be advantageous. In this study, we have analyzed the anti-inflammatory profile of three synthetic peptides first identified in skin secretion of the tree frog Hypsiboas raniceps. Structural characterization was performed using NMR spectroscopy and Mass Spectrometry, and the peptides were tested in vitro in RAW 264.7 cells and in vivo in Balb/c mice for their functional properties. The samples did not show a significant antimicrobial profile. NMR spectroscopy indicated that AC12 (ACFLTRLGTYVC) has a disulfide bond between C2 and C11 and a β-sheet-turn-β-sheet conformation in aqueous solution. This peptide showed no cytotoxic effect in mammalian cells and it was the most effective in reducing anti-inflammatory markers, such as NO, TNF-α and IL-12. Peptide DK16 (DKERPICSNTFRGRKC) demonstrated anti-inflammatory properties in vitro, while RC11 (RCFRRRGKLTC) significantly altered the cell viability in RAW 264.7 but was shown to be safe in Balb/c erythrocytes. Our results indicate that, of the three peptides studied, AC12 is the most efficient in reducing anti-inflammatory markers, and it could be a potential agent for the treatment of inflammatory diseases.

NMR solution structures of two mutants of desulforedoxin

The differences in geometry at the metal centres in the two known [Fe-4S] proteins rubredoxin (Rd) and desulforedoxin (Dx) are postulated to be a result of the different spacing of the C-terminal cysteine pair in the two proteins. In order to address this question, two mutants of Desulfovibrio gigas Dx with modified cysteinyl spacing were prepared and their solution structures have been determined by NMR. Mutant 1 of Dx (DxM1) has a single glycine inserted between the adjacent cysteines (C28 and C29) found in the wild type Dx sequence. Mutant 3 (DxM3) has two amino acid residues, -P-V-, inserted between C28 and C29 in order to mimic the primary sequence found in Rd from Desulfovibrio gigas. The solution structure of DxM1 exists, like wild type Dx, as a dimer in solution although the single glycine inserted between the adjacent cysteines disrupts the stability of the dimer resulting in exchange between a dimer state and a small population of another, probably monomeric, state. For DxM3 the two amino acid residues inserted between the adjacent cysteines results in a monomeric protein that has a global fold near the metal centre very similar to that found in Rd.

The solution structure and heme binding of the presequence of murine 5-aminolevulinate synthase

The mitochondrial import of 5-aminolevulinate synthase (ALAS), the first enzyme of the mammalian heme biosynthetic pathway, requires the N-terminal presequence. The 49 amino acid presequence transit peptide (psALAS) for murine erythroid ALAS was chemically synthesized, and circular dichroism and (1)H nuclear magnetic resonance (NMR) spectroscopies used to determine structural elements in trifluoroethanol/H(2)O solutions and micellar environments. A well defined amphipathic alpha-helix, spanning L22 to F33, was present in psALAS in 50% trifluoroethanol. Further, a short alpha-helix, defined by A5-L8, was also apparent in the 26 amino acid N-terminus peptide, when its structure was determined in sodium dodecyl sulfate. Heme inhibition of ALAS mitochondrial import has been reported to be mediated through cysteine residues in presequence heme regulatory motifs (HRMs). A UV/visible and (1)H NMR study of hemin and psALAS indicated that a heme-peptide interaction occurs and demonstrates, for the first time, that heme interacts with the HRMs of psALAS.

Characterization and differentiation of ruthenium(II) complexes with 1,4,7-trithiacyclononane and nitrogen heterocycles by electrospray mass spectrometry

Electrospray ionization mass spectrometry (ESIMS) was used to characterize a series of new ruthenium(II) complexes with several nitrogen heterocycles and a common ligand: the crown thioether 1,4,7-trithiacyclononane, [9]aneS(3). ESIMS allows the easy identification of the [Ru(II)Cl([9]aneS(3))Y]X complexes, where Y is a bidentate nitrogen heterocycle and X is Cl(-) or PF(6)(-), through the formation of two diagnostic ions by fragmentation of the common ligand [9]aneS(3). Structures for these ions and mechanisms for their gas-phase formation are proposed based on data from product ion spectra.

Enzymatic isolation and structural characterisation of polymeric suberin of cork from Quercus suber L

An enzymatic method has been used to isolate, for the first time, polymeric suberin from the bark of Quercus suber L. or cork. This was achieved by solvent extraction (dichloromethane, ethanol and water), followed by a step-by-step enzymatic treatment with cellulase, hemicellulase and pectinase, and a final extraction with dioxane/water. The progress of suberin isolation was monitored by Fourier transform infrared spectroscopy using a photoacoustic cell (FTIR-PAS). The material obtained (polymeric suberin (PS)) was characterised by solid-state and liquid-state nuclear magnetic resonance, FTIR-PAS and vapour pressure osmometry, and compared with the suberin fraction obtained by alkaline depolymerisation (depolymerised suberin (DS)). The results showed that PS is an aliphatic polyester of saturated and unsaturated fatty acids, with an average molecular weight (M(w)) of 2050 g mol(-1). Although this fraction represents only 10% of the whole suberin of cork, its polymeric nature gives valuable information about the native form of the polymer. DS was found to have an average M(w) of 750 g mol(-1) and to comprise a significant amount of acidic and alcoholic short aliphatic chains.

The solution structure of a [3Fe-4S] ferredoxin: oxidised ferredoxin II from Desulfovibrio gigas

The use of standard 2D NMR experiments in combination with 1D NOE experiments allowed the assignment of 51 of the 58 spin systems of oxidised [3Fe4S] ferredoxin isolated from Desulfovibrio gigas. The NMR solution structure was determined using data from 1D NOE and 2D NOESY spectra, as distance constraints, and information from the X-ray structure for the spin systems not detected by NMR in torsion angle dynamics calculations to produce a family of 15 low target function structures. The quality of the NMR family, as judged by the backbone r.m.s.d. values, was good (0.80 A), with the majority of phi/psi angles falling within the allowed region of the Ramachandran plot. A comparison with the X-ray structure indicated that the overall global fold is very similar in solution and in the solid state. The determination of the solution structure of ferredoxin II (FdII) in the oxidised state (FdIIox) opens the way for the determination of the solution structure of the redox intermediate state of FdII (FdII(int)), for which no X-ray structure is available.

NMR determination of the global structure of the 113Cd derivative of desulforedoxin: investigation of the hydrogen bonding pattern at the metal center

Desulforedoxin (Dx) is a simple homodimeric protein isolated from Desulfovibrio gigas (Dg) containing a distorted rubredoxin-like center with one iron coordinated by four cysteinyl residues (7.9 kDa with 36 amino acids per monomer). In order to probe the geometry and the H-bonding at the active site of Dx, the protein was reconstituted with 113Cd and the solution structure determined using 2D NMR methods. The structure of this derivative was initially compared with the NMR solution structure of the Zn form (Goodfellow BJ et al., 1996, J Biol Inorg Chem 1:341-353). Backbone amide protons for G4, D5, G13, L11 NH, and the Q14 NH side-chain protons, H-bonded in the X-ray structure, were readily exchanged with solvent. Chemical shift differences observed for amide protons near the metal center confirm the H-bonding pattern seen in the X-ray model (Archer M et al., 1995, J Mol Biol 251:690-702) and also suggest that H-bond lengths may vary between the Fe, Zn, and 113Cd forms. The H-bonding pattern was further probed using a heteronuclear spin echo difference (HSED) experiment; the results confirm the presence of NH-S H-bonds inferred from D2O exchange data and observed in the NMR family of structures. The presence of "H-bond mediated" coupling in Dx indicates that the NH-S H-bonds at the metal center have significant covalent character. The HSED experiment also identified an intermonomer "through space" coupling for one of the L26 methyl groups, indicating its proximity to the 113Cd center in the opposing monomer. This is the first example of an intermonomer "through space" coupling. Initial structure calculations produced subsets of NMR families with the S of C28 pointing away from or toward the L26 methyl: only the subset with the C28 sulfur pointing toward the L26 methyl could result in a "through space" coupling. The HSED result was therefore included in the structure calculations. Comparison of the Fe, Zn, and 113Cd forms of Dx suggests that the geometry of the metal center and the global fold of the protein does not vary to any great extent, although the H-bond network varies slightly when Cd is introduced. The similarity between the H-bonding pattern seen at the metal center in Dx, Rd (including H-bonded and through space-mediated coupling), and many zinc-finger proteins suggests that these H-bonds are structurally vital for stabilization of the metal centers in these proteins.