Citric acid/β-alanine carbon dots as a novel tool for delivery of plasmid DNA into E. coli cells

Successful delivery of plasmid DNA into the microbial cells is fundamental in recombinant DNA technology. Natural bacterial transformation is limited to only certain species due in part to the repulsive forces between negatively charged DNA and bacterial membranes. Most common method of DNA delivery into bacteria is artificial transformation through heat shock and electroporation. These methods require sophisticated instruments and tedious steps in preparation of competent cells. Transformation by conjugation is also not applicable to all plasmids. Nanoparticles have been used successfully in therapeutics for drug delivery into animal cells. They are starting to gain popularity in plant sciences as novel DNA nano carriers. Despite their promise as tool for DNA delivery, their use in microbial cell transformation has not been reported yet. Here we report the synthesis of carbon dots (CDs) from citric acid and β-alanine and their use in DNA delivery into E. coli cells. CDs were fabricated using microwave assisted synthesis. Plasmids carrying RFP reporter and ampicillin resistance genes were transferred to bacterial cells and further confirmed using polymerase chain reaction. Our findings indicate that CDs can be used successfully for delivery of foreign DNA of up to 10 kb into E. coli. We have demonstrated the use of β-alanine/citric acid carbon dots as nanocarriers of DNA into E. coli cells and identified their limitation in terms of the size of plasmid DNA they could carry. Use of these carbon dots is a novel method in foreign DNA delivery into bacterial cells and have a potential for the transformation of resistant organism for which there is still no reliable DNA delivery systems.

An improved fluorescent noncanonical amino acid for measuring conformational distributions using time-resolved transition metal ion FRET

With the recent explosion in high-resolution protein structures, one of the next frontiers in biology is elucidating the mechanisms by which conformational rearrangements in proteins are regulated to meet the needs of cells under changing conditions. Rigorously measuring protein energetics and dynamics requires the development of new methods that can resolve structural heterogeneity and conformational distributions. We have previously developed steady-state transition metal ion fluorescence resonance energy transfer (tmFRET) approaches using a fluorescent noncanonical amino acid donor (Anap) and transition metal ion acceptor to probe conformational rearrangements in soluble and membrane proteins. Here, we show that the fluorescent noncanonical amino acid Acd has superior photophysical properties that extend its utility as a donor for tmFRET. Using maltose-binding protein (MBP) expressed in mammalian cells as a model system, we show that Acd is comparable to Anap in steady-state tmFRET experiments and that its long, single-exponential lifetime is better suited for probing conformational distributions using time-resolved FRET. These experiments reveal differences in heterogeneity in the apo and holo conformational states of MBP and produce accurate quantification of the distributions among apo and holo conformational states at subsaturating maltose concentrations. Our new approach using Acd for time-resolved tmFRET sets the stage for measuring the energetics of conformational rearrangements in soluble and membrane proteins in near-native conditions.

Solid-Phase Synthesis of an Insect Pyrokinin Analog Incorporating an Imidazoline Ring as Isosteric Replacement of a trans Peptide Bond

A facile solid-phase synthetic method for incorporating the imidazoline ring motif, a surrogate for a trans peptide bond, into bioactive peptides is reported. The example described is the synthesis of an imidazoline peptidomimetic analog of an insect pyrokinin neuropeptide via a cyclization reaction of an iminium salt generated from the preceding amino acid and 2,4-diaminopropanoic acid (Dap).

Polypeptide formation in clusters of β-alanine amino acids by single ion impact

The formation of peptide bonds by energetic processing of amino acids is an important step towards the formation of biologically relevant molecules. As amino acids are present in space, scenarios have been developed to identify the roots of life on Earth, either by processes occurring in outer space or on Earth itself. We study the formation of peptide bonds in single collisions of low-energy He2+ ions (α-particles) with loosely bound clusters of β-alanine molecules at impact energies typical for solar wind. Experimental fragmentation mass spectra produced by collisions are compared with results of molecular dynamics simulations and an exhaustive exploration of potential energy surfaces. We show that peptide bonds are efficiently formed by water molecule emission, leading to the formation of up to tetrapeptide. The present results show that a plausible route to polypeptides formation in space is the collision of energetic ions with small clusters of amino acids.

Natural Deep Eutectic Solvent Extraction of Flavonoids of Scutellaria baicalensis as a Replacement for Conventional Organic Solvents

Natural deep eutectic solvents (NADES) are a type of ionic liquid (IL) or deep eutectic solvent (DES), the ingredients of which are exclusively natural products (non-toxic and environmentally friendly). Here, we explore the potential of NADES as an alternative to conventional organic solvents (e.g., aqueous methanol or ethanol) for the extraction of flavonoids from Scutellaria baicalensis stem bark to investigate their extractability depending on structural variation. Four NADES, each containing citric acid in combination with β-alanine, glucose, xylitol, or proline (at a molar ratio of 1:1), and a variable amount of water, were used to extract the flavonoid aglycones: baicalein (1), scutellarein (3), wogonin (5), and oroxylin A (7), and their glycosides, baicalin (2), scutellarin (4), wogonoside (6) and oroxyloside (8) from the powdered bark of S. baicalensis. The chemical profile and yield of the extracts were determined using HPTLC and HPLC. The extractability of individual flavonoids was found to be influenced by the concentration of water (20-60%, w/w) in the NADES. Among the tested flavonoids, the extraction yield of baicalein (1), scutellarein (3), wogonin (5), oroxylin A (7) with NADES was 2 to 6 times that of aqueous methanol. However, the amount of their corresponding glycosides (baicalin (2), wogonoside (6) and oroxyloside (8)) extracted with NADES was only 1.5-1.8 times higher than with aqueous methanol. Interestingly, the more hydrophilic glycosides were less extracted than their corresponding aglycones despite the high hydrophilicity of the NADES. These results prove that NADES may be used for extraction of compounds with a wide range of hydrophilicity.

Exploring ion-ion preferences through structure-property correlations: amino acid-derived, bis(guanidinium) disiloxane salts

In a more synthetical approach to the study of ion-specific phenomena, four dipodal bis(guanidinium) siloxanes have been synthesized starting from glycine, β-alanine, γ-aminobutanoic acid, L-proline and 1,3-bis(3-aminopropyl)tetramethyldisiloxane. Together with their non-amide progenitor they were comparatively studied in regards to their interactions with nine different anions: sulphate, chromate, molybdate, benzoate, chloride, azide, nitrite, nitrate and thiocyanate. Their aqueous solubilities, form, 1H NMR and FT-IR spectra were examined while searching for anion-specific interactions falling in- or outside of the Hofmeister series. We show that although the "chao-" and "kosmotropic" ions affect the properties of solutions in a predictable way, more selective cation-anion pairing is responsible for phase separation and crystallinity. As a prominent example, crystal structure of one of the benzoate salts was successfully obtained and reveals a synergy of hydrophobic packing, ionic and hydrogen bonding. Immobilized but still flexible siloxane bridges give rise to crystals described by P 42/n space group and neatly segregated into hydro- and lipophilic sections.

Isolation from Stevia rebaudiana of DMDP acetic acid, a novel iminosugar amino acid: synthesis and glycosidase inhibition profile of glycine and β-alanine pyrrolidine amino acids

DMDP acetic acid [N-carboxymethyl-2,5-dideoxy-2,5-imino-D-mannitol] 5 from Stevia rebaudiana is the first isolated natural amino acid derived from iminosugars bearing an N-alkyl acid side chain; it is clear from GCMS studies that such derivatives with acetic and propionic acids are common in a broad range of plants including mulberry, Baphia, and English bluebells, but that they are very difficult to purify. Reaction of unprotected pyrrolidine iminosugars with aqueous glyoxal gives the corresponding N-acetic acids in very high yield; Michael addition of both pyrrolidine and piperidine iminosugars and that of polyhydroxylated prolines to tert-butyl acrylate give the corresponding N-propionic acids in which the amino group of β-alanine is incorporated into the heterocyclic ring. These easy syntheses allow the identification of this new class of amino acid in plant extracts and provide pure samples for biological evaluation. DMDP N-acetic and propionic acids are potent α-galactosidase inhibitors in contrast to potent β-galactosidase inhibition by DMDP.

The molecular structure of β-alanine is resistant to sterilising doses of gamma radiation

β-alanine is the rate-limiting point for the endogenous synthesis of carnosine in skeletal muscle. Carnosine has a wide range of implications for health, normal function and exercise performance. Whilst the physiological relevance of carnosine to different tissues remains enigmatic, β-alanine administration is a useful strategy to investigate the physiological roles of carnosine in humans. Intravenous administration of β-alanine is an interesting approach to study carnosine metabolism. However, sterilisation is mandatory due to the nature of the administration route. We evaluated whether sterilising doses of gamma radiation damages the molecular structure and leads to the loss of functional characteristics of β-alanine. Pure β-alanine was sterilised by gamma radiation in sealed glass vials using a 60Co multipurpose irradiator at a dose rate of 8.5 kGy.hour-1 totalising 10, 20, 25 30 and 40 kGy. The molecular integrity was assessed by X-ray Diffraction and changes in content were determined by High Performance Liquid Chromatography (UV-HPLC) and Triple Quadrupole Mass Spectrometer (HPLC/MS-MS). Sterility assurance was evaluated by inoculation assay. To examine whether functional properties were preserved, β-alanine was infused in one participant, who rated the level of paraesthesia on the skin using a 0-3 scale. Urinary β-alanine was quantified before and 24-h following β-alanine infusion using HPLC-ESI+-MS/MS. Irradiation resulted in no change in the crystal structure of β-alanine, no degradation, and no new peaks were identified in the dose range assayed. The inoculation assay showed the absence of viable microorganisms in all β-alanine samples, including those that did not undergo irradiation. Intravenous infusion of β-alanine resulted in paraesthesia and it detected in the urine as per normal. We conclude that gamma radiation is a suitable technique for the sterilisation of β-alanine. It does not lead to degradation, damage to the β-alanine structure, content or loss of function within the evaluated irradiation conditions.

Synthesis of β-Peptide Standards for Use in Model Prebiotic Reactions

A one-pot method was developed for the preparation of a series of β-alanine standards of moderate size (2 to ≥12 residues) for studies concerning the prebiotic origins of peptides. The one-pot synthesis involved two sequential reactions: (1) dry-down self-condensation of β-alanine methyl ester, yielding β-alanine peptide methyl ester oligomers, and (2) subsequent hydrolysis of β-alanine peptide methyl ester oligomers, producing a series of β-alanine peptide standards. These standards were then spiked into a model prebiotic product mixture to confirm by HPLC the formation of β-alanine peptides under plausible reaction conditions. The simplicity of this approach suggests it can be used to prepare a variety of β-peptide standards for investigating differences between α- and β-peptides in the context of prebiotic chemistry.

Discovery and Preclinical Development of Netarsudil, a Novel Ocular Hypotensive Agent for the Treatment of Glaucoma

PURPOSE

Rho-associated protein kinase (ROCK) inhibitors lower intraocular pressure (IOP) by increasing aqueous outflow through the trabecular meshwork (TM). The preclinical characterization of netarsudil, a new ROCK/norepinephrine transporter (NET) inhibitor currently in clinical development, is presented herein.

METHODS

The kinase inhibitory activity of netarsudil was compared to its esterase metabolite, netarsudil-M1, and 3 other ROCK inhibitors using a commercially available kinase assay kit. Disruption of actin stress fibers was measured in primary porcine TM cells and disruption of focal adhesions in transformed human TM (HTM) cells. Induction of fibrosis markers after exposure to transforming growth factor-β2 (TGF-β2) was conducted in primary HTM cells. Ocular hypotensive activity and tolerability of topical formulations were evaluated in normotensive Dutch Belted rabbits and Formosan Rock monkeys. In vitro corneal metabolism assays were conducted using dog, pig, rabbit, monkey, and human corneas. In vivo ocular pharmacokinetics was studied in Dutch Belted rabbits.

RESULTS

Netarsudil inhibited kinases ROCK1 and ROCK2 with a Ki of 1 nM each, disrupted actin stress fibers and focal adhesions in TM cells with IC50s of 79 and 16 nM, respectively, and blocked the profibrotic effects of TGF-β2 in HTM cells. Netarsudil produced large reductions in IOP in rabbits and monkeys that were sustained for at least 24 h after once daily dosing, with transient, mild hyperemia observed as the only adverse effect.

CONCLUSION

Netarsudil is a novel ROCK/NET inhibitor with high potency in biochemical and cell-based assays, an ability to produce large and durable IOP reductions in animal models, and favorable pharmacokinetic and ocular tolerability profiles.

X-ray crystal structure of a malonate-semialdehyde dehydrogenase from Pseudomonas sp. strain AAC

The NAD-dependent malonate-semialdehyde dehydrogenase KES23460 from Pseudomonas sp. strain AAC makes up half of a bicistronic operon responsible for β-alanine catabolism to produce acetyl-CoA. The KES23460 protein has been heterologously expressed, purified and used to generate crystals suitable for X-ray diffraction studies. The crystals belonged to space group P212121 and diffracted X-rays to beyond 3 Å resolution using the microfocus beamline of the Australian Synchrotron. The structure was solved using molecular replacement, with a monomer from PDB entry 4zz7 as the search model.

How Anionic Vesicles Steer the Oligomerization of Enzymatically Oxidized p-Aminodiphenylamine (PADPA) toward a Polyaniline Emeraldine Salt (PANI-ES)-Type Product

The oxidation of the aniline dimer, p-aminodiphenylamine (PADPA), with Trametes versicolor laccase and O2 in an aqueous solution of pH 3.5 is controlled by negatively charged AOT (sodium bis(2-ethylhexyl) sulfosuccinate) vesicles. With vesicles, a product resembling polyaniline in its emeraldine salt form (PANI-ES) is obtained, in contrast to the reaction without vesicles where no such product is formed. To understand this observation, the product distribution and structures from the reaction with and without vesicles were determined by using partially selectively deuterated PADPA as a starting material and analyzing the products with HPLC-MS. We found that in the presence of vesicles the main product is obtained in about 50% yield, which is the N-C-para-coupled PADPA dimer that has spectroscopic properties of PANI-ES, as determined by time-dependent density functional theory (TD-DFT) calculations. A secondary reaction route leads to longer PADPA oligomers that must contain a phenazine core. Without vesicles, PADPA and its products undergo partial hydrolysis, but in the presence of vesicles, hydrolysis does not occur. Because molecular dynamics (MD) simulations show that the main intermediate oxidation product is embedded within the vesicle membrane, where the water content is very low, we propose that the microenvironment of the vesicle membrane protects the oxidation products from unwanted hydrolysis.

Diaminopropionic Acid Reinforced Graphene Sponge and Its Use for Hemostasis

2,3-Diaminopropionic acid (DapA), a medicinal amino acid, is used for the first time to prepare a DapA cross-linked graphene sponge (DCGS) for hemostasis treatment. In a comparison with the reported ethanediamine (EDA) cross-linked graphene sponge (CGS), this carboxyl-functionalized DCGS can not only quickly absorb plasma, but also stimulate erythrocytes and platelets to change their normal form and structure at the interface, which largely affects a cell's metabolism and biofunction, thus further promoting blood coagulation. Whole blood clotting and rat-tail amputation tests indicated that on the basis of the additional interfacial stimulation, the hemostatic efficiency of the DCGS has been significantly improved in comparison with that of the CGS control (P < 0.05). In-depth insight revealed that the increased oxidation degree and the negative charge density play the crucial rule in the enhanced hemostatic performance. The chiral effect contributes mainly to the selective adhesion of erythrocytes and platelets rather than practical hemostasis. Nevertheless, this presentation demonstrated that, on the premise of keeping the fast absorbability, this is an effective method to improve the hemostatic efficiency by enhancing the cell/graphene interface interaction.

Metal coordination and tyrosinase inhibition studies with Kojic-βAla-Kojic

Kojic acid is a natural antifungal and antibacterial agent that has been extensively studied for its tyrosinase inhibitory and metal coordination properties. Tyrosinase is a metalloenzyme with two copper ions in the active site. It is widely accepted that the tyrosinase inhibitory activity of kojic acid is related to its ability to coordinate metals. Over the past five years, we have used kojic acid to synthesize new and efficient bis-kojic acid chelators of iron and aluminium. In parallel, we investigated whether the de novo designed ligands could interfere with proper tyrosinase functioning. The present study combines our experience with inhibition and coordination studies of the new ligand: Kojic-βAla-Kojic. Research aimed at the assembly of a new potent tyrosinase inhibitor was based on the well-known crystal structure of the enzyme. Two questions were whether two kojic acids could act better than one and to what extent the length and kind of linker could ameliorate metal coordination, and inhibitory activity. Our results show that Kojic-βAla-Kojic has high affinity for Fe(III), Al(III), Zn(II), and Cu(II) and strong tyrosinase inhibitory effect and it can be proposed for use in industrial and pharmaceutical applications.

β-Alaninium tetrafluoroborate: a new salt with di-β-alaninium dimeric cation

β-Alaninium tetrafluoroborate crystallizes in the monoclinic system (space group P21/n, Z=4). The asymmetric unit contains one β-alaninium cation and one tetrafluoroborate anion, in which the fluorine atoms are disordered. All β-alaninium cations are connected with the symmetry related cations via an inversion center, thus forming dimeric centrosymmetric β-Ala(+)···β-Ala(+) cations. The O···O distance (2.698(2)Å) in the dimeric cation is relatively long compared to known distances of previously reported salts with A(+)···A(+) type dimeric cations. The infrared and Raman spectra are studied.

Global coagulation tests: their applicability for measuring direct factor Xa- and thrombin inhibition and reversal of anticoagulation by prothrombin complex concentrate

BACKGROUND

Specific mass spectrometry and direct activated factor X (Xa)- and thrombin inhibition assays do not allow determination of the reversal of anticoagulant effects of non-vitamin K direct oral anticoagulants (NOACs) by prothrombin complex concentrate (PCC). The objective of this study was the evaluation of the applicability of a variety of commercially available global coagulation assays in analyzing the reversal of NOAC anticoagulation by PCC.

METHODS

Plasma and whole blood were spiked with apixaban or dabigatran and PCC was added to these samples. Prothrombin time (PT), modified PT (mPT), activated partial prothrombin time (APTT), thrombography (CAT method) and thromboelastography (ROTEM, TEG) were performed.

RESULTS

Assays triggered by contact activation (APTT, INTEM) did not show inhibitor reversal by PCC. Assays triggered by tissue factor (TF) showed NOAC type and NOAC concentration dependent anticoagulation reversal effects of PCC ranging from partial normalization to overcorrection of the following parameters: clotting or reaction time (PT, mPT TEG-TF, EXTEM, FIBTEM); angle in thromboelastography (TEG-TF); thrombin generation (CAT) lag time, endogenous thrombin potential (ETP) and peak thrombin. Extent of reversal was assay reagent dependent. ETP (5 pM TF) was the only parameter showing complete reversal of anticoagulation by PCC for all NOACs ranging from 200 to 800 μg/L.

CONCLUSIONS

ETP fits with the concept that reversal assessment of NOAC anticoagulation by PCC should be based on measurements on the clotting potential or thrombin generating potential of the plasma or whole blood patient sample. Low sensitivity of ETP for NOACs and its correlation with bleeding are issues that remain to be resolved.

Potential grape-derived contributions to volatile ester concentrations in wine

Grape composition affects wine flavour and aroma not only through varietal compounds, but also by influencing the production of volatile compounds by yeast. C₉ and C₁₂ compounds that potentially influence ethyl ester synthesis during fermentation were studied using a model grape juice medium. It was shown that the addition of free fatty acids, their methyl esters or acyl-carnitine and acyl-amino acid conjugates can increase ethyl ester production in fermentations. The stimulation of ethyl ester production above that of the control was apparent when lower concentrations of the C₉ compounds were added to the model musts compared to the C₁₂ compounds. Four amino acids, which are involved in CoA biosynthesis, were also added to model grape juice medium in the absence of pantothenate to test their ability to influence ethyl and acetate ester production. β-Alanine was the only one shown to increase the production of ethyl esters, free fatty acids and acetate esters. The addition of 1 mg∙L⁻¹ β-alanine was enough to stimulate production of these compounds and addition of up to 100 mg∙L⁻¹ β-alanine had no greater effect. The endogenous concentrations of β-alanine in fifty Cabernet Sauvignon grape samples exceeded the 1 mg∙L⁻¹ required for the stimulatory effect on ethyl and acetate ester production observed in this study.

Role of the osmolyte taurine on the folding of a model protein, hen egg white lysozyme, under a crowding condition

Taurine is one of the osmolytes that maintain the structure of proteins in cells exposed to denaturing environmental stressors. Recently, cryoelectron tomographic analysis of eukaryotic cells has revealed that their cytoplasms are crowded with proteins. Such crowding conditions would be expected to hinder the efficient folding of nascent polypeptide chains. Therefore, we examined the role of taurine on the folding of denatured and reduced lysozyme, as a model protein, under a crowding condition. The results confirmed that taurine had a better effect on protein folding than did β-alanine, which has a similar chemical structure, when the protein to be folded was present at submillimolar concentration. NMR analyses further revealed that under the crowding condition, taurine had more interactions than did β-alanine with the lysozyme molecule in both the folded and denatured states. We concluded that taurine improves the folding of the reduced lysozyme at submillimolar concentration to allow it to interact more favorably with the lysozyme molecule. Thus, the role of taurine, as an osmolyte in vivo, may be to assist in the efficient folding of proteins.

γT -S195A thrombin reduces the anticoagulant effects of dabigatran in vitro and in vivo

BACKGROUND

Dabigatran etexilate (DE) is an oral direct thrombin inhibitor used to prevent strokes in patients with atrial fibrillation. No licensed DE antidote is currently available. We hypothesized that active site-mutated S195A thrombin (S195A-IIa) and/or its trypsinized derivative (γT -S195A-IIa) would sequester dabigatran, the active form of DE, and reduce its anticoagulant effects.

OBJECTIVE

To assess active site-mutated S195A or γT -S195A-IIa as dabigatran reversal agents in vitro and in vivo.

METHODS

Diluted thrombin time (dTT) assays were performed using human or murine plasma containing dabigatran, combined with S195A-IIa, γT -S195A-IIa or FPR-chloromethyl ketone-treated thrombin (FPR-IIa). Bleeding times were determined in anesthetized DE-treated mice also receiving γT -S195A-IIa or vehicle 15 min prior to tail transection. The time to occlusion of carotid arteries of DE-treated mice also receiving S195A-IIa, γT -S195A-IIa, prothrombin complex concentrate (PCC) or vehicle, 15 min prior to topical FeCl3 , was determined using Doppler ultrasound.

RESULTS

γT-S195A-IIa reduced dTT values of dabigatran-containing human and murine plasma more effectively than S195-IIa; FPR-IIa had no effect. A dose of 13 mg kg(-1) DE abrogated occlusive thrombus formation in the carotid arteries of FeCl3 -treated mice; γT -S195A-IIa (6 mg kg(-1) ) or PCC (14.3 IU kg(-1) ), but not saline vehicle or S195A-IIa (6 mg kg(-1) ), was equally effective in restoring thrombus formation. Bleeding times of mice treated with 60 mg kg(-1) DE and γT -S195A-IIa (6 mg kg(-1) ) or saline vehicle did not differ.

CONCLUSIONS

Our data suggest that γT -S195A-IIa decreases the anticoagulant effects of dabigatran in vitro and is partially effective at restoring hemostasis-related thrombus formation in DE-treated mice in vivo.

Agronomic characterization and α- and β-ODAP determination through the adoption of new analytical strategies (HPLC-ELSD and NMR) of ten sicilian accessions of grass pea

Ten accessions of grass pea (Lathyrus sativus L.) from different Sicilian sites, cultivated in the same environmental conditions, were analyzed for their morphological and productive parameters and for the content of two non-protein amino acids: α- and β-ODAP (α- and β-N-oxalyl-l-α,β-diaminopropionic acid). The β-isomer is the neurotoxin responsible for the neuron disease known as lathyrism. This analysis was carried out using two common analytical methodologies never applied in their determination, an HPLC separation with evaporative light scattering (ELS) as detector, and nuclear magnetic resonance (NMR). The content of the two isomers falls in the range reported for these compounds: 0.42-0.74 and 2.69-4.59 g/kg for α- and β-ODAP, respectively; and the two methods yield comparable results. High productivity and a high protein content were detected in three Sicilian accessions. Low β-ODAP content was found to be linked to accessions with heavier seeds and those originating at lower altitudes.

Chlorogenic acid increased acrylamide formation through promotion of HMF formation and 3-aminopropionamide deamination

This research was aimed to investigate why chlorogenic acid, presents at high concentrations in some food raw material, influences acrylamide formation. In the asparagine/glucose Maillard reaction system (pH=6.8), addition of chlorogenic acid significantly increased acrylamide formation and inhibited its elimination. In contrast, the quinone derivative of chlorogenic acid decreased acrylamide formation. Three mechanisms may be involved for increasing acrylamide formation by chlorogenic acid. Firstly, it increased the formation of HMF, which acts as a more efficient precursor than glucose to form acrylamide. Secondly, it decreased activation energy for conversion of 3-aminopropionamide (3-APA) to acrylamide (from 173.2 to 136.6kJ/mol), and enhances deamination from 3-APA. And thirdly, it prevented attack of the produced acrylamide from free radicals by keeping high redox potential during the Maillard reaction.

The synthesis and characterization of hydroxyapatite-β-alanine modified by grafting polymerization of γ-benzyl-L-glutamate-N-carboxyanhydride

In this study, hydroxyapatite (HAP) was surface-modified by the addition of β-alanine (β-Ala), and the ring-opening polymerization of γ-benzyl-l-glutamate-N-carboxy-anhydride (BLG-NCA) was subsequently initiated. HAP containing surface poly-γ-benzyl-l-glutamates (PBLG) was successfully prepared in this way. With the increase of PBLG content in HAP-PBLG, the solubility of HAP-PBLG increased gradually and it was ultimately soluble in chloroform. HAP-PLGA with surface carboxyl groups was obtained by the catalytic hydrogenation of HAP-PBLG. In the process of HAP modification, the morphology changes from rod to sheet and from flake to needle. The effect of BLG-NCA concentration on the character of hydroxyapatite-β-alanine-poly(γ-benzyl-l-glutamate) (HAP-PBLG) was investigated. The existence of amino acids on the HAP surfaces was confirmed in the resulting Fourier transform infrared (FTIR) spectra. The resulting powder X-ray diffraction patterns indicated that the crystallinity of HAP decreased when the ratio of BLG-NCA/HAP-NH₂ increased to 20/1. Transmission electron microscopy (TEM) indicated that the particle size of HAP-PBLG decreased significantly and that the resulting particles appeared less agglomerated relative to that of the HAP-NH₂ crystals. Furthermore, ¹H-NMR spectra and FTIR spectra revealed that hydroxyapatite-β-alanine-poly (l-glutamic acid) (HAP-PLGA) was able to successfully bear carboxylic acid groups on its side chains.

Nucleation kinetics, growth and studies of β-alanine single crystals

Solubility and metastable zone width for the re-crystallized salt of β-alanine was determined. Induction period measurement for the selected supersaturation ratios at room temperature (31 °C) was carried out for supersaturated aqueous solutions of β-alanine and it is noticed that induction period decreases with increase of supersaturation ratio. The nucleation parameters such as Gibbs free energy change, radius and number of molecules of the critical nucleus, interfacial tension and the nucleation rate have been evaluated by classical nucleation theory. Single crystals of β-alanine were grown using the optimized nucleation parameters by solution method and grown crystals have been subjected to various studies like XRD studies, FTIR, optical, thermal and SHG studies.

Neuron-shaped gold nanocrystals and two-dimensional dendritic gold nanowires fabricated by use of a long-chain amidoamine derivative

We report the synthesis of two-dimensional (2D) dendritic Au nanowires (DNWs) with diameters of 100-200 nm in an aqueous solution of long-chain amidoamine derivative (C18AA), which acted as both capping and reducing agent, and the preparation of large 2D DNWs with diameters of 400-700 nm by seeded growth of the original DNWs. The seeded growth method in the presence of C18AA enables the fabrication of novel neuron-shaped Au nanostructures consisting of two DNWs dangling from both ends of an ultrathin Au nanowire.

Transition metal complexes bearing flexible N₃ or N₃O donor ligands: reactivity toward superoxide radical anion and hydrogen peroxide

Mononuclear complexes of N-methylpropanoate-N,N-bis-(2-pyridylmethyl)amine (MPBMPA) and N-propanoate-N,N-bis-(2-pyridylmethyl)amine (HPBMPA) with first row transition metals from Mn to Cu were synthesized and characterized by spectroscopy (infrared, UV-visible), electrochemistry (cyclic voltammetry), microanalysis and in four cases X-ray crystallography. Structure of the complexes revealed high flexibility of these ligands that can adopt facial (Fe) and meridional (Cu) geometry. Activity in the degradation of reactive oxygen species (superoxide radical anion: superoxide dismutase (SOD)-like activity and hydrogen peroxide: catalase-like activity) was tested throughout the complex series in aqueous solutions. In connection with the catalytic dismutation of H(2)O(2), bleaching tests with morin were also conducted in water. Comparison of the two ligands helped in elucidating the possible role of the carboxylate moiety in the different catalytic reactions. Although no general trends could be revealed between reactivity and constitution of the first coordination sphere, plausible explanations for differences are discussed individually for SOD like, catalase-like and bleaching activity.

Dabigatran (Pradaxa)

Dabigatran (Pradaxa) is a member of the relatively new class of antithrombotic drugs known as direct thrombin inhibitors (DTIs). It may supplant warfarin (Coumadin) in a number of applications as it may produce a more predictable, potent, and immediate anticoagulant effect, with fewer significant side effects and interactions, and requires less monitoring.

Selective N-alkylation of β-alanine facilitates the synthesis of a poly(amino acid)-based theranostic nanoagent

The development of functional amino acid-based polymeric materials is emerging as a platform to create biodegradable and nontoxic nanomaterials for medical and biotechnology applications. In particular, facile synthetic routes for these polymers and their corresponding polymeric nanomaterials would have a positive impact in the development of novel biomaterials and nanoparticles. However, progress has been hampered by the need to use complex protection-deprotection methods and toxic phase transfer catalysts. In this study, we report a facile, single-step approach for the synthesis of an N-alkylated amino acid as an AB-type functional monomer to generate a novel pseudo-poly(amino acid), without using the laborious multistep, protection-deprotection methods. This synthetic strategy is reproducible, easy to scale up, and does not produce toxic byproducts. In addition, the synthesized amino acid-based polymer is different from conventional linear polymers as the butyl pendants enhance its solubility in common organic solvents and facilitate the creation of hydrophobic nanocavities for the effective encapsulation of hydrophobic cargos upon nanoparticle formation. Within the nanoparticles, we have encapsulated a hydrophobic DiI dye and a therapeutic drug, Taxol. In addition, we have conjugated folic acid as a folate receptor-targeting ligand for the targeted delivery of the nanoparticles to cancer cells expressing the folate receptor. Cell cytotoxicity studies confirm the low toxicity of the polymeric nanoparticles, and drug-release experiments with the Taxol-encapsulated nanoparticles only exhibit cytotoxicity upon internalization into cancer cells expressing the folate receptor. Taken together, these results suggested that our synthetic strategy can be useful for the one-step synthesis of amino acid-based small molecules, biopolymers, and theranostic polymeric nanoagents for the targeted detection and treatment of cancer.

Crystal and molecular structure of N-(4-nitrophenyl)-β-alanine--its vibrational spectra and theoretical calculations

The N-(4-nitrophenyl)-β-alanine in crystalline form directly by the addition of 4-nitroaniline to the acrylic acid in aqueous solution has been obtained. The title β-alanine derivative crystallizes in the P2(1)/c space group of monoclinic system with four molecules per unit cell. The X-ray geometry of β-alanine derivative molecule has been compared with those obtained by molecular orbital calculations corresponding to the gas phase. In the crystal the molecules related by an inversion center interact via symmetrically equivalent O-H···O hydrogen bonds with O···O distance of 2.656(2) Å forming a dimeric structure. The dimers of β-alanine derivative weakly interact via N-H···O hydrogen bonds between the H atom of β-amine groups and one of O atom of nitro groups. The room temperature powder vibrational (infrared and Raman) measurements are in accordance with the X-ray analysis. In aqueous solution of 4-nitroaniline and acrylic acid, the double CC bond of vinyl group of acrylic acid breaks as result of 4-nitroaniline addition.

Kinetics of sorption-desorption of benfuracarb insecticide in mollisols

BACKGROUND

Sorption-desorption processes govern the movement of pesticides in soil. These processes determine the potential hazard of the pesticide in a given environment for groundwater contamination and need to be investigated.

RESULTS

In the present study, sorption-desorption processes of benfuracarb were investigated using a batch method in two mollisols. The kinetics of benfuracarb sorption in mollisols conformed to two-compartment (1 + 1) first-order kinetics. The fast sorption rate constant was about 3 times higher for silt loam than for loam soil. However, the slow sorption rate constants were statistically similar for both soils. The concentration-dependent sorption-desorption isotherms of benfuracarb could not closely conform to the Freundlich isotherm in mollisols of high organic C content. The computed values of both the sorption (log K) and desorption (log K') capacities were higher for silt loam than for loam soil. The desorption index (n'/n) values in the range 30.0-41.3 indicated poor reversibility of sorbed benfuracarb in mollisols.

CONCLUSION

In view of the strong sorption of benfuracarb in mollisols with only partial desorption, the possibility of the leaching of soil-applied benfuracarb to contaminate groundwaters appears to be low.

Acquisition of Raman spectra of amino acids using portable instruments: outdoor measurements and comparison

Raman spectra of 13 amino acids: L-alanine, β-alanine, L-asparagine, L-aspartic acid, L-glutamic acid, L-glutamine, glycine, L-methionine, L-proline, L-serine, L-threonine, L-tryptophan and L-tyrosine were acquired outdoors using two portable Raman instruments from the Ahura and Delta Nu manufacturers, both with 785 nm laser excitation. Both instruments provide quality Raman spectra with nevertheless a variable dependence upon the prevailing experimental conditions. The data acquired in these experiments will inform the selection of suitable Raman spectrometers for the in-field detection of biomolecules of relevance to the search for life signatures spectroscopically in terrestrial extreme environments and in extraterrestrial exploration, especially of planetary surfaces and subsurfaces using robotic instrumentation.

A new 18F-labeled BBN-RGD peptide heterodimer with a symmetric linker for prostate cancer imaging

A peptide heterodimer comprises two different receptor-targeting peptide ligands. Molecular imaging probes based on dual-receptor targeting peptide heterodimers exhibit improved tumor targeting efficacy for multi-receptor expressing tumors compared with their parent single-receptor targeting peptide monomers. Previously we have developed bombesin (BBN)-RGD (Arg-Gly-Asp) peptide heterodimers, in which BBN and RGD are covalently connected with an asymmetric glutamate linker (J Med Chem 52:425-432, 2009). Although (18)F-labeled heterodimers showed significantly better microPET imaging quality than (18)F-labeled RGD and BBN monomers in a PC-3 xenograft model which co-expresses gastrin-releasing peptide receptor (GRPR) and integrin αvβ3, tedious heterodimer synthesis due to the asymmetric nature of glutamate linker restricts their clinical applications. In this study, we report the use of a symmetric linker AEADP [AEADP = 3,3'-(2-aminoethylazanediyl)dipropanoic acid] for the synthesis of BBN-RGD peptide heterodimer. The (18)F-labeled heterodimer ((18)F-FB-AEADP-BBN-RGD) showed comparable microPET imaging results with glutamate linked BBN-RGD heterodimers, indicating that the replacement of glutamate linker with AEADP linker did not affect the biological activities of BBN-RGD heterodimer. The heterodimer synthesis is rather easy and straightforward. Because tumors often co-express multiple receptors, the use of a symmetric linker provides a general method of fast assembly of various peptide heterodimers for imaging multi-receptor expressing tumors.

Ecotoxicity and genotoxicity assessment of cytotoxic antineoplastic drugs and their metabolites

In spite of growing scientific concern about pharmaceuticals in the environment, there is still a lack of information especially with regard to their metabolites. The present study investigated ecotoxicity and genotoxicity of three widely used cytostatic agents 5-fluorouracil (5-FU), cytarabine (CYT) and gemcitabine (GemC) and their major human metabolites, i.e. alpha-fluoro-beta-alanine (FBAL), uracil-1-beta-D-arabinofuranoside (AraU) and 2',2'-difluorodeoxyuridine (dFdU), respectively. Effects were studied in acute immobilization and reproduction assays with crustacean Daphnia magna and growth inhibition tests with alga Desmodesmus subspicatus and bacteria Pseudomonas putida. Genotoxicity was tested with umu-test employing Salmonella choleraesius subsp. chol. Toxicity was relatively high at parent compounds with EC(50) values ranging from 44 microg L(-1) (5-fluorouracil in the P. putida test) to 200 mg L(-1) (cytarabine in D. magna acute test). In general, the most toxic compound was 5-FU. Studied metabolites showed low or no toxicity; only FBAL (metabolite of 5-FU) showed low toxicity to D. subspicatus and P. putida with EC(50) values 80 and 140 mg L(-1), respectively. All parent cytostatics showed genotoxicity with minimum genotoxic concentrations (MGC) ranging from 40 to 330 mg L(-1). From metabolites, only FBAL was genotoxic in high concentrations. To our knowledge, the present study provides some of the first ecotoxicity data for both cytostatics and their metabolites, which might further serve for serious evaluation of ecological risks. The observed EC(50) values within the microg L(-1) range were fairly close to concentrations reported in hospital sewage water, which indicates further research needs, especially studies of chronic toxicity.

Validation of an isocratic HPLC method to detect 2-fluoro-beta-alanine for the analysis of dihydropyrimidine dehydrogenase activity

The efficacy of the chemotherapeutic drug 5'-fluorouracil is reduced by catabolism to 2'-fluoro-beta-alanine (FBAL), a three-step reaction in which dihydropyrimidine dehydrogenase (DPD) catalyzes the rate-limiting step. To study in vitro DPD activity, we developed and validated an isocratic, reverse-phase HPLC method to detect and quantify FBAL without using multiple columns or radiolabeled substrates. Pre-column derivatization of FBAL was performed using o-phthalaldehyde in the presence of two sulfur donors, ethanthiol or beta-mercaptoethanol, and the resulting products assayed. Calibration curves were linear over a range of 10-200 microg/ml and the method was successfully applied to the examination of DPD activity in cultured cells.

QSAR, docking studies and pharmacophore identification of phenylmethyl phenoxy propyl amino propanoic acid derivatives as leukotriene A4 hydrolase inhibitors

The enzyme leukotriene A4 (LTA4) plays an important role as precursor of slow reactive substances as LTC4, LTD4, and LTE4. It is an attractive target for molecular modeling and QSAR study. Our effort is mainly focused on exploring the SAR for inhibitors of the LTA4 hydrolase through docking study, pharmacophore modeling and molecular descriptor study. The binding of these small molecules on LTA4 hydrolase enzyme was described by the models developed on 2D molecular descriptors, with good predictive power (39 compounds, 6 descriptors, r2 0.98, SEE 0.167, F-value 268.53, q2 0.90, r2 adj 0.97, P-value < 0.0001, SD of residuals 0.15). Docking studies were employed to presume the probable binding conformation of these analogues and exploring the SAR for the compounds. The novel pharmacophore represents the ligand features that are involved in interactions with the target protein, as well as the space around the ligand occupied by the protein. The efforts are aimed to discover the SAR for the inhibitors of LTA4 hydrolase through techniques of QSAR, docking and pharmacophore.

Rapid Ti(III) reduction of perchlorate in the presence of beta-alanine: kinetics, pH effect, complex formation, and beta-alanine effect

Ti(III) reduction of perchlorate might be a useful method for the treatment of highly perchlorate-contaminated water. Though the reaction rate was usually low, we observed that beta-alanine (HOOCCH(2)CH(2)NH(2)) could significantly promote the reaction. A complete (>99.9%) perchlorate removal was obtained in a solution containing [ClO(4)(-)]=1.0mM, [Ti(III)]=40 mM, and [beta-alanine]=120 mM after 2.5h of reaction under 50 degrees C. The effects of both pH and complex formation on the reaction were then studied. The results showed that without beta-alanine the optimal pH was 2.3. When pH increased from 1.6 to 2.3, the reduction rate increased remarkably. In the pH range >2.3, however, the reduction was significantly inhibited, attributed to the formation of Ti(III) precipitate. The presence of beta-alanine at a molar ratio of [beta-alanine]:[Ti(III)]=3:1 significantly increased the reduction rate of perchlorate even at near neutral pH. This is because beta-alanine formed complexes with Ti(III), which greatly improved the total soluble [Ti(III)] in the pH range between 3.5 and 6. The findings may lead to the development of rapid treatment methods for intermittent and small stream of highly perchlorate-contaminated water, which are resulted from the manufacturing, storage, handling, use and/or disposal of large quantities of perchlorate salts.

Fate of benfuracarb insecticide in mollisols and brinjal crop

The fate of benfuracarb was studied under field conditions in brinjal fruits and soil following foliar spray application at 0.25 and 0.50 microg g(-1) by HPLC. At 0.25 microg g(-1), benfuracarb persisted up to 7 days both in soil and brinjal but at 0.50 microg g(-1), benfuracarb residues persisted up to 10 and 12 days in soil and brinjal fruits, respectively. The persistence of benfuracarb residues, both in soil and brinjal, followed first-order kinetics. The half-life values of benfuracarb in soil and brinjal fruit were found to be 3.54 and 3.90 days at 0.25 microg g(-1) and 3.75 and 4.73 days at 0.50 microg g(-1), respectively.

Role of 1alpha,25(OH)2 vitamin D3 on alpha-[1-(14)C]MeAIB accumulation in immature rat testis

1,25D3 is critical for the maintenance of normal reproduction since reduced fertility is observed in male rats on a vitamin D-deficient diet. Vitamin D-deficient male rats have incomplete spermatogenesis and degenerative testicular changes. In the present study we have examined the ionic involvement and intracellular messengers of the stimulatory effect of 1,25D3 on amino acid accumulation in immature rat testis. 1,25D3 stimulates amino acid accumulation from 10(-12) to 10(-6) M by increasing the slope to reach a maximum value at 10(-10) M, as compared to the control group. No effect was observed at a lower dose (10(-13) M). Time-course showed an increase on amino acid accumulation after 15, 30, and 60 min of incubation with 1,25D3 (10(-10) M). 1,25D3 stimulated amino acid accumulation in 11-day-old rat testis but not in testis that were 20 days old. Cycloheximide totally blocked the 1,25D3 action on amino acid accumulation. Furthermore, a localized elevation of cAMP increased the stimulatory effect of 1,25D3 and the blockage of PKA nullified the action of the hormone. In addition, 1,25D3 action on amino acid accumulation was also mediated by ionic pathways, since verapamil and apamine diminished the hormone effect. The stimulatory effect of 1,25D3 on amino acid accumulation is age-dependent and specific to this steroidal hormone since testosterone was not able to change amino acid accumulation in both ages studied. This study provides evidence for a dual effect for 1,25D3, pointing to a genomic effect that can be triggered by PKA, as well as to a rapid response involving Ca2+/K+ channels on the plasma membrane.

Antifungal activity of thionated analogues of Nva-FMDP and Lys-Nva-FMDP

The antifungal activity of synthetic endothiopeptdides, i.e. Nva(psi)[CSNH]-FMDP and Lys(psi)[CSNH]-Nva(psi)[CSNH]-FMDP was studied in medium containing blood serum, against selected Candida strains; Candida albicans Gu4 (fluconazole sensitive), C. albicans Gu5 (fluconazole resistant), C. albicans ATCC 10231, Candida krusei DSM 6128 and Candida parapsilosis DSM 5784. Although thiopeptide bonds in the tested peptides increased their stability in blood serum, their antifungal activity, however, drastically decreased in comparison with the peptides containing non-modified peptide bonds. Moreover, the inhibitory activity towards glucosamine-6-phosphate synthase of thionated synthetic analogue of FMDP was performed. The thiopeptdide bond also influenced its inhibitory properties against enzyme from C. albicans.

Can alpha- and beta-alanine containing peptides be distinguished based on the CID spectra of their protonated ions?

The fragmentation reactions of isomeric dipeptides containing alpha- and beta-alanine residues (alphaAla-alphaAla, alphaAla-betaAla, betaAla-alphaAla, and betaAla-betaAla) were studied using a combination of low-energy and energy resolved collision induced dissociation (CID). Each dipeptide gave a series of different fragment ions, allowing for differentiation. For example, peptides containing an N-terminal beta-Ala residue yield a diagnostic imine loss, while lactam ions at m/z 72 are unique to peptides containing beta-Ala residues. In addition, MS(3) experiments were performed. Structure-specific fragmentation reactions were observed for y(1) ions, which help identify the C-terminal residue. The MS(3) spectra of the b(2) ions are different suggesting they are unique for each peptide. Density functional theory (DFT) calculations predict that b(2) ions formed via a neighboring group attack by the amide are thermodynamically favored over those formed via neighboring group attack by the N-terminal amine. Finally, to gain further insight into the unique fragmentation chemistry of the peptides containing an N-terminal beta-alanine residue, the fragmentation reactions of protonated beta-Ala-NHMe were examined using a combination of experiment and DFT calculations. The relative transition-state energies involved in the four competing losses (NH(3), H(2)O, CH(3)NH(2), and CH(2)=NH) closely follow the relative abundances of these as determined via CID experiments.

Formation of [b3 - 1 + cat]+ ions from metal-cationized tetrapeptides containing beta-alanine, gamma-aminobutyric acid or epsilon-aminocaproic acid residues

The presence and position of a single beta-alanine (betaA), gamma-aminobutyric acid (gammaABu) or epsilon-aminocaproic acid (Cap) residue has been shown to have a significant influence on the formation of b(n)+ and y(n)+ product ions from a series of model, protonated peptides. In this study, we examined the effect of the same residues on the formation of analogous [b3 - 1 + cat]+ products from metal (Li+, Na+ and Ag+)-cationized peptides. The larger amino acids suppress formation of b3+ from protonated peptides with general sequence AAXG (where X = beta-alanine, gamma-aminobutyric acid or epsilon-aminocaproic acid), presumably because of the prohibitive effect of larger cyclic intermediates in the 'oxazolone' pathway. However, abundant [b3 - 1 + cat]+ products are generated from metal-cationized versions of AAXG. Using a group of deuterium-labeled and exchanged peptides, we found that formation of [b3 - 1 + cat]+ involves transfer of either amide or alpha-carbon position H atoms, and the tendency to transfer the atom from the alpha-carbon position increases with the size of the amino acid in position X. To account for the transfer of the H atom, a mechanism involving formation of a ketene product as [b3 - 1 + cat]+ is proposed.

Novel Long-circulating Liposomes Containing Peptide Library-lipid Conjugates: Synthesis andIn VivoBehavior

Rapid uptake of intravenously injected liposomes by the mononuclear phagocyte system has limited their use as drug delivery vehicles. Recently, various long-circulating liposomes have been prepared by incorporating glycolipids or other amphiphilic molecules into the lipid bilayer of conventional liposomes. The purpose of the present study was to design a new class of biodegradable membrane modifiers that would increase the half-life of liposomes in vivo. Using solid-phase peptide synthesis, synthesized were 30-residue random libraries consisting of a random sequence of glycine, beta-alanine and gamma-aminobutyric acid. The libraries were coupled to stearic acid (SA) or phosphatidylethanolamine (PE). The resulting amphiphilic conjugates were mixed with egg phosphatidylcholine (PC) and cholesterol (Chol) in a 6:47:47 ratio, and unilamellar liposomes were prepared. For comparison, plain PC/Chol (50:50) liposomes, as well as liposomes containing polyethylene glycol (PEG)-SA/PC/Chol (6:47:47) and PEG-PE/PC/Chol (6:47:47) were also prepared. Calcein was entrapped in the liposomes, which were given intravenously to rats at a dose of 9.2 mumol lipid/kg, and the amount of intact liposomes present in serum was followed with time. While the conventional liposomes had a short elimination half-life (28 min), the liposomes modified with library-PE had a much longer half-life (170 min), while library-SA provided no improvement of the liposome pharmacokinetics. PEG-PE greatly improved the half-life of the liposomes (400 min) while PEG-SA only provided a marginal improvement. All liposome preparations were cleared in a biphasic fashion. In conclusion, a novel biodegradable lipopeptide conjugate was designed that endows liposomes with a prolonged circulation time in vivo. The pharmacokinetic profile of these modified liposomes was drastically improved over that of conventional liposomes. Since the library is prepared by solid-phase synthesis, length and/or composition could easily be modified in order to modulate the clearance profile of the liposomes. Tailoring of the pharmacokinetic profile of the liposomes depending on their intended application may allow for a greater flexibility of use than PEG-PE.

β-Alanine suppresses heat inactivation of lactate dehydrogenase

Beta-Alanine exhibits neurotransmitter activity and is a component of the anti-glycation agent carnosine. We propose that beta-alanine may have additional properties which may be of physiological significance. Interestingly, stress modulates the level of beta-alanine, which regulates excitotoxicity responses and prevents neuronal cell death. We hypothesize that beta-alanine's protective role may involve preservation of enzyme structure and function, suggesting that beta-alanine may act as a chemical chaperone. We used light scattering, enzyme activity and intrinsic fluorescence to monitor heat-induced changes in lactate dehydrogenase (LDH) in the presence and absence of beta-alanine. We observed that beta-alanine suppressed heat-induced LDH inactivation, prevented LDH aggregation, ameliorated the decrease in intrinsic fluorescence and reactivated thermally denatured LDH. These observations support the hypothesis that beta-alanine has chaperone-like activity and may play a cellular role in the preservation of enzyme function.

L-2,3-diaminopropionate: one of the building blocks for the biosynthesis of Zwittermicin A in Bacillus thuringiensis subsp. kurstaki strain YBT-1520

Zwittermicin A (ZwA) is a hybrid polyketide-non-ribosomal peptide that is thought to be biosynthesized from five proposed building blocks, including the 2,3-diaminopropionate. Candidate genes for de novo biosynthesis of 2,3-diaminopropionate, zwa5A and zwa5B, have been identified in a previous study. In this research, zwa5A was interrupted and chemically synthesized 2,3-diaminopropionate was used to feed the zwa5A(-) mutant. Results showed that feeding with 2,3-diaminopropionate restored the ability of the zwa5A(-) mutant to produce ZwA. Another non-ribosomal peptide synthase gene, designated orf3, was identified. Amino acid dependent PPi release assay showed that the adenylation domain ZWAA2 of ORF3 acyl-adenylated l-2,3-diaminopropionate effectively. Taken together, it can be concluded that l-2,3-diaminopropionate is indeed one of the building blocks for the biosynthesis of Zwittermicin A.

Solution structure of a novel D-naphthylalanine substituted peptide with potential antibacterial and antifungal activities

A new type of Trp-rich peptide, Ac-KWRRWVRWI-NH2, designated as Pac-525, was found to possess improved activity against both gram-positive and negative bacteria. We have synthesized two Pac-525 analogues, D-Pac-525 containing all D-amino acids and D-Nal-Pac-525, the D-Pac-525 analogue with tryptophan replaced by D-beta-naphthylalanine. We have determined the solution structure of D-Nal-Pac-525 bound to membrane-mimetic DPC micelles by two-dimensional NMR methods. The DPC micelle-bound structure of D-Nal-Pac-525 adopts a left-hand alpha-helical segment and the positively charged residues are clustered together to form a hydrophilic patch. The surface electrostatic potential map indicates the three D-beta-naphthylalanines are packed against the peptide backbone and form an amphipathic structure. A variety of biophysical and biochemical experiments, including circular dichroism, fluorescence spectroscopy, and microcalorimetry, were used to show that D-Nal-Pac-525 interacted strongly with negatively charged phospholipid vesicles and induced efficient dye release from these vesicles, suggesting that the strong antimicrobial activity of D-Nal-Pac-525 may be due to interactions with bacterial and fungus membranes.

Conformational variability of the glycine receptor M2 domain in response to activation by different agonists

Models describing the structural changes mediating Cys loop receptor activation generally give little attention to the possibility that different agonists may promote activation via distinct M2 pore-lining domain structural rearrangements. We investigated this question by comparing the effects of different ligands on the conformation of the external portion of the homomeric alpha1 glycine receptor M2 domain. Conformational flexibility was assessed by tethering a rhodamine fluorophore to cysteines introduced at the 19' or 22' positions and monitoring fluorescence and current changes during channel activation. During glycine activation, fluorescence of the label attached to R19'C increased by approximately 20%, and the emission peak shifted to lower wavelengths, consistent with a more hydrophobic fluorophore environment. In contrast, ivermectin activated the receptors without producing a fluorescence change. Although taurine and beta-alanine were weak partial agonists at the alpha1R19'C glycine receptor, they induced large fluorescence changes. Propofol, which drastically enhanced these currents, did not induce a glycine-like blue shift in the spectral emission peak. The inhibitors strychnine and picrotoxin elicited fluorescence and current changes as expected for a competitive antagonist and an open channel blocker, respectively. Glycine and taurine (or beta-alanine) also produced an increase and a decrease, respectively, in the fluorescence of a label attached to the nearby L22'C residue. Thus, results from two separate labeled residues support the conclusion that the glycine receptor M2 domain responds with distinct conformational changes to activation by different agonists.

Chiroptical properties of diamino carboxylic acids

Diamino carboxylic acids have recently come to the attention of scientists working in the field of early life and its development. These are the monomers of a hypothetic early form of genetic material, the so-called Peptide Nucleic Acid (PNA) (Nielson et al., Proc Natl Acad Sci USA 2000;97:3868-3871). Since all biopolymers rely on a specific handedness of their building blocks, the question of symmetry breaking occurs in diamino acids and PNA in the same way as in amino acids and proteins. One possible mechanism for triggering this, is asymmetric photochemistry in interstellar/circumstellar matter by means of circularly polarized light (Bailey et al., Science 2005;281:672-674; Bailey, Orig Life Evol Biosphere 2001;21:167-183; Buschermöhle, Astrophys J 2005;624:821-826; Meierhenrich, Angew Chem Int Ed Engl 2005;44:5630-5634). Here we have measured the CD-spectra of four chiral diamino carboxylic acids, three of which were found in the Murchison meteorite (Meierhenrich, Proc Natl Acad Sci USA 2004;101:9182-9186). The spectra show a uniform peak at 200 nm. These results and additional quantum mechanical calculations of the involved molecular orbitals support the assumption that the process of symmetry breaking in diamino acids does not depend significantly on the length of the side chain. This means that one process alone could suffice to lead to symmetry breaking in all four measured diamino carboxylic acids and might even to some extent be transferable to monoamino acids, the monomers of proteins.

Cell-penetrating peptides as transporters for morpholino oligomers: effects of amino acid composition on intracellular delivery and cytotoxicity

Arginine-rich cell-penetrating peptides (CPPs) are promising transporters for intracellular delivery of antisense morpholino oligomers (PMO). Here, we determined the effect of L-arginine, D-arginine and non-α amino acids on cellular uptake, splice-correction activity, cellular toxicity and serum binding for 24 CPP−PMOs. Insertion of 6-aminohexanoic acid (X) or β-alanine (B) residues into oligoarginine R₈ decreased the cellular uptake but increased the splice-correction activity of the resulting compound, with a greater increase for the sequences containing more X residues. Cellular toxicity was not observed for any of the conjugates up to 10 μM. Up to 60 μM, only the conjugates with ⩾ 5 Xs exhibited time- and concentration-dependent toxicity. Substitution of L-arginine with D-arginine did not increase uptake or splice-correction activity. High concentration of serum significantly decreased the uptake and splice-correction activity of oligoarginine conjugates, but had much less effect on the conjugates containing X or B. In summary, incorporation of X/B into oligoarginine enhanced the antisense activity and serum-binding profile of CPP−PMO. Toxicity of X/B-containing conjugates was affected by the number of Xs, treatment time and concentration. More active, stable and less toxic CPPs can be designed by optimizing the position and number of R, D-R, X and B residues.

Synthesis of β-alanine C60 derivative and its protective effect on hydrogen peroxide-induced apoptosis in rat pheochromocytoma cells

Oxidative stress has been considered as a major cause of cellular injuries in a variety of clinical abnormalities, especially prominent in neural diseases. One of the effective ways to prevent the reactive oxygen species (ROS) mediated cellular injury is dietary or pharmaceutical augmentation of some free radical scavenger. Water-soluble amino-fullerene derivative is a novel compound that behaves as a free radical scavenger with excellent biocompatibility. In the present study, we synthesized a novel beta-alanine C(60) derivative. The product was characterized by FT-IR, (1)H NMR, (13)C NMR, LC-MS and elemental analysis. We investigated the protective effect on hydrogen peroxide-induced oxidative stress and apoptotic death in cultured rat pheochromocytoma (PC12) cells. PC12 cells treated with hydrogen peroxide underwent apoptotic death determined by MTT, flow cytometry analysis and PI/Hoechst 33342 staining. Moreover, the scavenging ability of beta-alanine C(60) derivative to reactive oxygen species both in vivo and in vitro of PC12 cells was measured. The results suggest that beta-alanine C(60) derivative has the potential to prevent oxidative stress-induced cell death without evident toxicity. Hence, on the basis of the above-mentioned studies, we can hypothesize that the protective effect of beta-alanine C(60) derivative on H(2)O(2) induced apoptosis is related to their known scavenger activity toward ROS.

Synthesis and NMR characterization of β-alanine-bridged hemispherodextrin, a very efficient chiral selector in EKC

A capped derivative of beta-CD (THALAH) was synthesized and characterized by NMR spectroscopy at different pH values. A trehalose moiety, bonded through beta-alanine bridges to the CD cavity, is included in the capping unit, giving peculiar properties to this molecule. The hemispherodextrin thus obtained was tested as a chiral selector in EKC. At neutral pH, the monocationic species of THALAH behaves as a very efficient selector separating successfully all the 11 tested enantiomeric pairs of dansyl-derivatives of amino acids, some of them even at concentrations as low as 0.15 mM. The differences observed in the migration order among the different systems give suggestions about the mechanism of molecular recognition between the selector and the analytes.

Variable stability heterodimeric coiled-coils from manipulation of electrostatic interface residue chain length

The design of variable-stability coiled-coil heterodimers is described. The electrostatic interface between helices, formed by contact between side chains in heptad e/g positions, is manipulated to produce complexes ranging in stability from ones that are essentially unstructured to those that cannot be thermally denatured. The tuning is accomplished by incremental extension or contraction of parent glutamic acid and lysine side chains by single methylene units, producing peptides that bear either carboxylic acids or amines separated from the peptide backbone by one to four CH2 groups. Detailed examination of all homodimers and electrostatically compatible heterodimers generates interesting combinations, particularly those in which longer-chain acids are incorporated into peptides paired with lysine-bearing ones. The discovery of very stable dimers allows exchange experiments in which one strand of an original heterodimer is specifically replaced by an added one, even in cases where the original complex features the native-like glutamic acid/lysine pairing. The reported results add significantly to the available design templates for coiled-coil construction and enable the future implementation of various triggered-recognition strategies.