Salivary Hydrogen Sulfide Measured with a New Highly Sensitive Self-Immolative Coumarin-Based Fluorescent Probe

Ample evidence suggests that H₂S is an important biological mediator, produced by endogenous enzymes and microbiota. So far, several techniques including colorimetric methods, electrochemical analysis and sulfide precipitation have been developed for H₂S detection. These methods provide sensitive detection, however, they are destructive for tissues and require tedious sequences of preparation steps for the analyzed samples. Here, we report synthesis of a new fluorescent probe for H₂S detection, 4-methyl-2-oxo-2H-chromen-7-yl 5-azidopentanoate (1). The design of 1 is based on combination of two strategies for H₂S detection, i.e., reduction of an azido group to an amine in the presence of H₂S and intramolecular lactamization. Finally, we measured salivary H₂S concentration in healthy, 18–40-year-old volunteers immediately after obtaining specimens. The newly developed self-immolative coumarin-based fluorescence probe (C₁₅H₁₅N₃O₄) showed high sensitivity to H₂S detection in both sodium phosphate buffer at physiological pH and in saliva. Salivary H₂S concentration in healthy volunteers was within a range of 1.641–7.124 μM.

Disruption of Kcc2-dependent inhibition of olfactory bulb output neurons suggests its importance in odour discrimination

Synaptic inhibition in the olfactory bulb (OB), the first relay station of olfactory information, is believed to be important for odour discrimination. We interfered with GABAergic inhibition of mitral and tufted cells (M/T cells), the principal neurons of the OB, by disrupting their potassium-chloride cotransporter 2 (Kcc2). Roughly, 70% of mice died around 3 weeks, but surviving mice appeared normal. In these mice, the resulting increase in the intracellular Cl(-) concentration nearly abolished GABA-induced hyperpolarization of mitral cells (MCs) and unexpectedly increased the number of perisomatic synapses on MCs. In vivo analysis of odorant-induced OB electrical activity revealed increased M/T cell firing rate, altered phasing of action potentials in the breath cycle and disrupted separation of odour-induced M/T cell activity patterns. Mice also demonstrated a severely impaired ability to discriminate chemically similar odorants or odorant mixtures. Our work suggests that precisely tuned GABAergic inhibition onto M/T cells is crucial for M/T cell spike pattern separation needed to distinguish closely similar odours.

Serum Albumin Domain Structures in Human Blood Serum by Mass Spectrometry and Computational Biology

Chemical cross-linking combined with mass spectrometry has proven useful for studying protein-protein interactions and protein structure, however the low density of cross-link data has so far precluded its use in determining structures de novo. Cross-linking density has been typically limited by the chemical selectivity of the standard cross-linking reagents that are commonly used for protein cross-linking. We have implemented the use of a heterobifunctional cross-linking reagent, sulfosuccinimidyl 4,4'-azipentanoate (sulfo-SDA), combining a traditional sulfo-N-hydroxysuccinimide (sulfo-NHS) ester and a UV photoactivatable diazirine group. This diazirine yields a highly reactive and promiscuous carbene species, the net result being a greatly increased number of cross-links compared with homobifunctional, NHS-based cross-linkers. We present a novel methodology that combines the use of this high density photo-cross-linking data with conformational space search to investigate the structure of human serum albumin domains, from purified samples, and in its native environment, human blood serum. Our approach is able to determine human serum albumin domain structures with good accuracy: root-mean-square deviation to crystal structure are 2.8/5.6/2.9 Å (purified samples) and 4.5/5.9/4.8Å (serum samples) for domains A/B/C for the first selected structure; 2.5/4.9/2.9 Å (purified samples) and 3.5/5.2/3.8 Å (serum samples) for the best out of top five selected structures. Our proof-of-concept study on human serum albumin demonstrates initial potential of our approach for determining the structures of more proteins in the complex biological contexts in which they function and which they may require for correct folding. Data are available via ProteomeXchange with identifier PXD001692.

Synthesis, Crystal Structure and Biological Activity Screening of Novel N-(α-Bromoacyl)-α-amino Esters Containing Valyl Moiety

Three novel N-(α-bromoacyl)-α-amino esters: methyl 2-(2-bromo-3-methylbutanamido)pentanoate (1), methyl 2-(2-bromo-3-methylbutanamido)-2-phenylacetate (2) and methyl 2-(2-bromo-3-methylbutanamido)-3-phenylpropanoate (3) were synthesized. Single crystal X-ray diffraction data are reported for compounds 1 and 2. The cytotoxicity, antiinflammatory and antibacterial activity of compounds 1-3 were investigated. Additionally, the physico-chemical properties of studied compounds were calculated and an in silico toxicological study of compounds 1-3 was performed. The low level of cytotoxicity and absence of antibacterial and anti-inflammatory activity of 1-3 in tested concentrations might be a beneficial prerequisite for their incorporation in prodrugs.

Reactions of Cl atoms with alkyl esters: kinetic, mechanism and atmospheric implications

Rate coefficients have been measured for the reaction of Cl atoms with a series of alkyl esters at 298 ± 2 K and atmospheric pressure in a large volume photoreactor using the relative kinetic technique. The kinetic data have been used in conjunction with other literature studies on the reactions of Cl atoms with esters to revise the existing values for ester substituent factors in a structure activity relationship (SAR) for Cl reactions. Product studies are reported for the reactions of Cl atoms with isopropyl ethanoate and methyl-2-methyl-propanoate under NO x -free conditions. These studies highlight the types of products that can be expected when oxidation occurs at R groups on the acyl (-C(O)OR) and oxy (RC(O)O-) sides of the ester functionality where R is a straight or branched chain alkyl entity. Possible atmospheric repercussions of the atmospheric chemistry of esters are considered.

Chemical characterization and anaerobic biodegradability of hydrothermal liquefaction aqueous products from mixed-culture wastewater algae

This study examined the chemical characteristics and the anaerobic degradability of the aqueous product from hydrothermal liquefaction (HTL-ap) from the conversion of mixed-culture algal biomass grown in a wastewater treatment system. The effects of the HTL reaction times from 0 to 1.5 h, and reaction temperatures from 260 °C to 320 °C on the anaerobic degradability of the HTL-ap were quantified using biomethane potential assays. Comparing chemical oxygen demand data for HTL-ap from different operating conditions, indicated that organic matter may partition from organic phase to aqueous phase at 320 °C. Moderate lag phase and the highest cumulative methane production were observed when HTL-ap was obtained at 320 °C. The longest lag phase and the smallest production rate were observed in the process fed with HTL-ap obtained at 300 °C. Nevertheless, after overcoming adaptation issues, this HTL-ap led to the second highest accumulated specific methane production. Acetogenesis was identified as a possible rate-limiting pathway.

Coating gigaporous polystyrene microspheres with cross-linked poly(vinyl alcohol) hydrogel as a rapid protein chromatography matrix

Gigaporous polystyrene (PS) microspheres were hydrophilized by in situ polymerization to give a stable cross-linked poly(vinyl alcohol) (PVA) hydrogel coating, which can shield proteins from the hydrophobic PS surface underneath. The amination of microspheres (PS-NH2) was first carried out through acetylization, oximation and reduction, and then 4,4'-azobis (4-cyanovaleric acid) (ACV), a polymerization initiator, was covalently immobilized on PS-NH2 through amide bond formation, and the cross-linked poly(vinyl acetate) (PVAc) was prepared by radical polymerization at the surfaces of ACV-immobilized PS microspheres (PS-ACV). Finally, the cross-linked PVA hydrogel coated gigaporous PS microspheres (PS-PVA) was easily achieved through alcoholysis of PVAc. Results suggested that the PS microspheres were effectively coated with cross-linked PVA hydrogel, where the gigaporrous structure remained under optimal conditions. After hydrophilic modification (PS-PVA), the protein-resistant ability of microspheres was greatly improved. The hydroxyl-rich PS-PVA surface can be easily derivatized by classical chemical methods. Performance advantages of the PS-PVA column in flow experiment include good permeability, low backpressure, and mechanical stability. These results indicated that PS-PVA should be promising in rapid protein chromatography.

Cell attachment on poly(3-hydroxybutyrate)-poly(ethylene glycol) copolymer produced by Azotobacter chroococcum 7B

BACKGROUND

The improvement of biomedical properties, e.g. biocompatibility, of poly(3-hydroxyalkanoates) (PHAs) by copolymerization is a promising trend in bioengineering. We used strain Azotobacter chroococcum 7B, an effective producer of PHAs, for biosynthesis of not only poly(3-hydroxybutyrate) (PHB) and its main copolymer, poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHB-HV), but also alternative copolymer, poly(3-hydroxybutyrate)-poly(ethylene glycol) (PHB-PEG).

RESULTS

In biosynthesis we used sucrose as the primary carbon source and valeric acid or poly(ethylene glycol) 300 (PEG 300) as additional carbon sources. The chemical structure of PHB-PEG and PHB-HV was confirmed by 1H nuclear-magnetic resonance (1H NMR) analysis. The physico-chemical properties (molecular weight, crystallinity, hydrophilicity, surface energy) and surface morphology of films from PHB copolymers were studied. To study copolymers biocompatibility in vitro the protein adsorption and COS-1 fibroblasts growth on biopolymer films by XTT assay were analyzed. Both copolymers had changed physico-chemical properties compared to PHB homopolymer: PHB-HV and PHB-PEG had less crystallinity than PHB; PHB-HV was more hydrophobic than PHB in contrast to PHB-PEG appeared to have greater hydrophilicity than PHB; whereas the morphology of polymer films did not differ significantly. The protein adsorption to PHB-PEG was greater and more uniform than to PHB and PHB-PEG copolymer promoted better growth of COS-1 fibroblasts compared with PHB homopolymer.

CONCLUSIONS

Thus, despite low EG-monomers content in bacterial origin PHB-PEG copolymer, this polymer demonstrated significant improvement in biocompatibility in contrast to PHB and PHB-HV copolymers, which may be coupled with increased protein adsorption and hydrophilicity of PEG-containing copolymer.

Ionic-liquid-catalyzed efficient transformation of γ-valerolactone to methyl 3-pentenoate under mild conditions

Green nylons! Acidic ionic-liquid catalysis for the transformation of γ-valerolactone into methyl 3-pentenoate (M3P) is shown to be performed efficiently under mild conditions. M3P is obtained selectively from a reaction at 170 °C for 3.5 h in the presence of an acidic ionic liquid that has a low vapor pressure, high thermal stability, and excellent catalytic performance. A possible reaction pathway for this conversion is also presented.

UV resonance Raman spectroscopy monitors polyglutamine backbone and side chain hydrogen bonding and fibrillization

We utilize 198 and 204 nm excited UV resonance Raman spectroscopy (UVRR) and circular dichroism spectroscopy (CD) to monitor the backbone conformation and the Gln side chain hydrogen bonding (HB) of a short, mainly polyGln peptide with a D(2)Q(10)K(2) sequence (Q10). We measured the UVRR spectra of valeramide to determine the dependence of the primary amide vibrations on amide HB. We observe that a nondisaggregated Q10 (NDQ10) solution (prepared by directly dissolving the original synthesized peptide in pure water) exists in a β-sheet conformation, where the Gln side chains form hydrogen bonds to either the backbone or other Gln side chains. At 60 °C, these solutions readily form amyloid fibrils. We used the polyGln disaggregation protocol of Wetzel et al. [Wetzel, R., et al. (2006) Methods Enzymol.413, 34-74] to dissolve the Q10 β-sheet aggregates. We observe that the disaggregated Q10 (DQ10) solutions adopt PPII-like and 2.5(1)-helix conformations where the Gln side chains form hydrogen bonds with water. In contrast, these samples do not form fibrils. The NDQ10 β-sheet solution structure is essentially identical to that found in the NDQ10 solid formed upon evaporation of the solution. The DQ10 PPII and 2.5(1)-helix solution structure is essentially identical to that in the DQ10 solid. Although the NDQ10 solution readily forms fibrils when heated, the DQ10 solution does not form fibrils unless seeded with the NDQ10 solution. This result demonstrates very high activation barriers between these solution conformations. The NDQ10 fibril secondary structure is essentially identical to that of the NDQ10 solution, except that the NDQ10 fibril backbone conformational distribution is narrower than in the dissolved species. The NDQ10 fibril Gln side chain geometry is more constrained than when NDQ10 is in solution. The NDQ10 fibril structure is identical to that of the DQ10 fibril seeded by the NDQ10 solution.

Distribution and organoleptic impact of ethyl 2-hydroxy-4-methylpentanoate enantiomers in wine

The enantiomers of ethyl 2-hydroxy-4-methylpentanoate (ethyl dl-leucate) were assayed in several wines using chiral gas chromatography (γ-cyclodextrin). Analyses of 55 commercial wines from various vintages and origins revealed different distributions. Generally, white wines presented only the R form, whereas red wines contained both enantiomers, in various ratios according to aging. The highest levels of the S form were found in the oldest samples. The R/S average enantiomeric ratio of this compound in red wine was approximately 95:5 with an average total concentration of ∼400 μg/L. The olfactory threshold of R-ethyl 2-hydroxy-4-methylpentanoate (126 μg/L) in hydroalcoholic solution was almost twice that of the S form (55 μg/L). The olfactory threshold of a mixture of R- and S-ethyl 2-hydroxy-4-ethylpentanoate (95:5, m/m) in hydroalcoholic solution was 51 μg/L, suggesting that both enantiomeric forms contribute to perception of this compound in wine, resulting in a synergistic effect. Both enantiomers have quite similar aromatic nuances. Sensory analysis was employed to demonstrate a synergistic effect of this ethyl ester on the perception of fruity aromas in wine: in hydroalcoholic solution supplemented with R- or S-ethyl 2-hydroxy-4-methylpentanoate or a mixture of the R and S forms (95:5, m/m) at their average concentrations in red wines, fruity character was perceived at concentrations 2.2, 4.5, and 2.5 times lower, respectively, than in hydroalcoholic solution alone. Sensory profiles of aromatic reconstitutions, using HPLC fruity fractions, highlighted the contribution of this compound to blackberry fruit and fresh fruit descriptors.

Homogeneous catalysis of valeronitrile hydrolysis under supercritical conditions

Supercritical nitrile hydrolysis can be used for both, amide and acid production as well as waste water treatment, as the hydrolysis products show good biodegradability. The conventional process at ambient conditions requires large amounts of mineral acid or base. Approaches that use supercritical water as a green solvent without a catalyst have been investigated over recent years. Findings for valeronitrile hydrolysis presented recently showed promising reaction rates and valeric acid yields. In an attempt to further maximize product yield and to better understand the impact of the pH, reactions in dilute sulfuric acid (0.01 mol L(-1)) were performed in a continuous high-pressure laboratory-scale apparatus at 400-500 °C, 30 MPa, and a maximum residence time of 100 s. Results from both reaction media were compared with regard to productivity and sustainability.

Synthesis and characterization of PHV-block-mPEG diblock copolymer and its formation of amphiphilic nanoparticles for drug delivery

Despite the recent research interest in the field of nanoparticles delivery system, their structure modification and transport behavior of various hydrophobic drugs is poorly developed. In this article the synthesis of novel amphiphilic diblock copolymer poly([R]-3-hydroxyvalerate)-block-monomethoxy poly(ethylene glycol) (PHV-block-mPEG) was undertaken by modifying the structure of biodegradable and hydrophobic poly([R]-3-hydroxyvalerate) (PHV) with hydrophilic monomethoxy poly(ethylene glycol) (mPEG). The chemical combination of the two blocks was carried out in the melt using bis(2-ethylhexanoate) tin as transesterification catalyst. The synthesized product was characterized by gel permeation chromatography (GPC), 1H nuclear magnetic resonance (NMR) and differential scanning calorimetry (DSC) analysis. The block copolymer self-assembled into amphiphilic nanoparticles with a core of hydrophobic PHV and a shell of hydrophilic mPEG in aqueous solution. Characterization of the nanoparticles showed the formation of discrete, spherically shaped nanoparticles with mean particle size of 200 +/- 1 nm and zeta potential of -14 +/- 1 mV. A hydrophobic drug thymoquinone was efficiently incorporated into the core hydrophobic domain of the nanoparticles and its release kinetics was studied in vitro. The amphiphilic PEGylated nanoparticles showed biocompatibility when checked in neuronal hippocampal cells of prenatal rat. Our results suggest that the amphiphilic nanoparticles with core-shell structures are potentially useful to develop novel drug carriers.

[Composite biodegradable materials based on polyhydroxyalkanoate]

Conditions for the processing and mixing of biodegradable polymers at temperatures less than their thermal destruction (130-150 degrees C) using standard equipment have been identified. The structure of the polyhydroxybutyrate/valerate (PHB/V) copolymer has been revealed and peculiarities of the crystal phase formation at different monomer ratios have been investigated. It was shown that pure PHB with molecular mass 180-270 kDa has elastic module approximately 1.2 GPa, strength approximately 25 MPa, and elongation at break approximately 10%. The most active biodestructors of PHB, PHB/V, and their composites have been selected (Aspergillus caespitosus), and the ability of basidiomycete Panus tigrinus to biodegrade polyalkanoates was demonstrated for the first time. It was shown that A. caespitosus degraded PHB/V and Biopol films along with the PHB with the destruction rate depending on the technology of the film production, on the molecular mass, and on the extend of the polymer crystallinity.

Polar 3-alkylidene-5-pivaloyloxymethyl-5'-hydroxymethyl-gamma-lactones as protein kinase C ligands and antitumor agents

A series of DAG-lactones with polar 3-alkylidene substituents have been investigated as PKC-alpha ligands and antitumor agents. Extensive analysis of structure-activity relationships for the 3-alkylidene chain revealed that polar groups such as ether, hydroxyl, aldehyde, ester, acyloxy, and amido were tolerated with similar binding affinities and reduced lipophilicities compared to the corresponding unsubstituted alkylidene chain. Among the derivatives, compounds 5, 6 and 8 with an ether type of side chain showed high binding affinities in range of K(i)= 3-5 nM and excellent antitumor profiles, particularly against the colo205 colon cancer and the K562 leukemia cell lines.

Reversible Addition−Fragmentation Chain Transfer Polymerization of N-Isopropylacrylamide: A Comparison between a Conventional and a Fast Initiator

The reversible addition-fragmentation chain transfer (RAFT) polymerization of N-isopropylacrylamide (NIPAM) was studied to determine the reasons for deviation of experimental molecular weights to lower molecular weight at high monomer conversion when S-1-dodecyl-S-(alpha,alpha'-dimethyl-alpha' '-acetic acid)trithiocarbonate (CTAm) and S,S-bis(alpha,alpha'-dimethyl-alpha' '-acetic acid)trithiocarbonate (CTAd) were used as RAFT agents at 65 degrees C. For this purpose, experiments were performed in N,N'-dimethylformamide (DMF) at the NIPAM/CTA ratio of 200 with initiators capable of yielding fast and slow initiation, respectively by photochemical and thermal process, either at ambient temperature or at 65 degrees C. When the polymerization of NIPAM was conducted under these conditions with Irgacure-2959 (IRGC) as photoinitiator, a continuing supply of primary radicals by incremental initiator addition was required to achieve reasonably high conversion. This effect was also apparent by the loss of linearity of the first-order kinetic plot with a conventional initiator (4,4-azobis(4-cyanovaleric acid) (ACVA) as azo-initiator, 10h (t1/2) decomposition at 65 degrees C) indicating that steady-state concentration of the macroradical decreases significantly with the initiator consumption. Nevertheless, polymers with predictable number-average molecular weight Mn (i.e., based on [monomer]/([CTA] + [initiator]) ratio) and narrow polydispersities were obtained (PDIs << 1.2) with CTAm indicating that the process of chain growth was controlled. When CTAd was used, instead of CTAm, the polymers obtained were characterized by a larger polydispersity (1.2 < PDIs < 1.3). The so-called "living steady-state concentration" in chain equilibration together with the linear dependence of Mn vs conversion was observed only when the 200/1 NIPAM/CTA mixture in DMF was subjected to a permanent photoirradiation at 65 degrees C. With ACVA, the deviation of the experimentally measured molecular weights at high conversion was accounted for by the simultaneous self-initiated polymerization of NIPAM with the controlled process in the presence of CTA at 65 degrees C. Similar drift from the linear dependence Mn vs conversion was also observed at 65 degrees C when a significant number of low molecular weight polymer chains were generated intentionally by photodecomposition of IRGC.

Nanostructured biosensor for measuring neuropathy target esterase activity

Neuropathy target esterase (NTE) is a membrane protein found in human neurons and other cells, including lymphocytes. Binding of certain organophosphorus (OP) compounds to NTE is believed to cause OP-induced delayed neuropathy (OPIDN), a type of paralysis for which there is no effective treatment. Mutations in NTE have also been linked with serious neurological diseases, such as motor neuron disease. This paper describes development of the first nanostructured biosensor interface containing a catalytically active fragment of NTE known as NEST. The biosensor was fabricated using the layer-by-layer assembly approach, by immobilizing a layer of NEST on top of multilayers consisting of a polyelectrolyte (poly-L-lysine) and an enzyme (tyrosinase). The biosensor has a response time on the order of seconds and gives a concentration-dependent decrease in sensor output in response to a known NEST (and NTE) inhibitor. Potential applications of the biosensor include screening OP compounds for NTE inhibition and investigating the enzymology of wild-type and mutant forms of NTE. Although the development of a NEST biosensor was the primary purpose of this study, we found that the approach developed for NEST could also be extended to measure the activity of other esterases involved in neural processes, such as acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). On the basis of measured sensitivities, phenyl valerate was the preferred substrate for NEST and BChE, whereas phenyl acetate was better for AChE.

Determination of kinetic parameters for interfacial enzymatic reactions on self-assembled monolayers

This paper reports a method to characterize the kinetic constants for the action of enzymes on immobilized substrates. This example uses cutinase, a serine esterase that hydrolyzes 4-hydroxyphenyl valerate moieties that are immobilized on a self-assembled monolayer of alkanethiolates on gold. The product of the enzyme reaction is a hydroquinone, which is redox active and therefore permits the use of cyclic voltammetry to monitor the extent of reaction in situ. A kinetic model based on the Michaelis-Menten formalism is used to analyze the dependence of initial rates of reaction on both the substrate density and the enzyme concentration. The resulting value of k(cat)/K(M) for the interfacial reaction is comparable to that for a homogeneous phase reaction with a substrate of similar structure. This strategy of using monolayers presenting substrates for the enzyme and cyclic voltammetry to measure reaction rates provides quantitative and real-time information on reaction rates and permits a level of analysis of interfacial enzyme reactions that to date has been difficult to realize.

Hydrolysis of pyrethroids by human and rat tissues: examination of intestinal, liver and serum carboxylesterases

Hydrolytic metabolism of pyrethroid insecticides in humans is one of the major catabolic pathways that clear these compounds from the body. Rodent models are often used to determine the disposition and clearance rates of these esterified compounds. In this study the distribution and activities of esterases that catalyze pyrethroid metabolism have been investigated in vitro using several human and rat tissues, including small intestine, liver and serum. The major esterase in human intestine is carboxylesterase 2 (hCE2). We found that the pyrethroid trans-permethrin is effectively hydrolyzed by a sample of pooled human intestinal microsomes (5 individuals), while deltamethrin and bioresmethrin are not. This result correlates well with the substrate specificity of recombinant hCE2 enzyme. In contrast, a sample of pooled rat intestinal microsomes (5 animals) hydrolyze trans-permethrin 4.5-fold slower than the sample of human intestinal microsomes. Furthermore, it is demonstrated that pooled samples of cytosol from human or rat liver are approximately 2-fold less hydrolytically active (normalized per mg protein) than the corresponding microsomal fraction toward pyrethroid substrates; however, the cytosolic fractions do have significant amounts (approximately 40%) of the total esteratic activity. Moreover, a 6-fold interindividual variation in carboxylesterase 1 protein expression in human hepatic cytosols was observed. Human serum was shown to lack pyrethroid hydrolytic activity, but rat serum has hydrolytic activity that is attributed to a single CE isozyme. We purified the serum CE enzyme to homogeneity to determine its contribution to pyrethroid metabolism in the rat. Both trans-permethrin and bioresmethrin were effectively cleaved by this serum CE, but deltamethrin, esfenvalerate, alpha-cypermethrin and cis-permethrin were slowly hydrolyzed. Lastly, two model lipase enzymes were examined for their ability to hydrolyze pyrethroids. However, no hydrolysis products could be detected. Together, these results demonstrate that extrahepatic esterolytic metabolism of specific pyrethroids may be significant. Moreover, hepatic cytosolic and microsomal hydrolytic metabolism should each be considered during the development of pharmacokinetic models that predict the disposition of pyrethroids and other esterified compounds.

Towards ‘bio-based’ Nylon: conversion of γ-valerolactone to methyl pentenoate under catalytic distillation conditions

Methyl pentenoate, a promising Nylon intermediate, is produced in >95% yield via the transesterification of gamma-valerolactone, a bio-based intermediate, under catalytic distillation conditions.

Synthesis of lipophilic 2-oxoamides based on γ-aminobutyric and δ-aminovaleric analogues and their activity against phospholipase A2

A variety of lipophilic 2-oxoamides based on gamma-aminobutyric and delta-aminovaleric analogues were synthesized. 2-oxoamides containing a tetrazole, a thioethyl or a thioacetyl group are weak inhibitors of GIVA cPLA(2), while derivatives containing a methyl tetrazole, a diethyl phosphonate or a thioethyl group are weak inhibitors of GV sPLA(2).

Redesign of human carbonic anhydrase II for increased esterase activity and specificity towards esters with long acyl chains

The effect of modulating the shape and the size of the hydrophobic pocket on the esterase activity and specificity of human carbonic anhydrase II (HCAII) for esters with different acyl chain lengths was investigated. Following an initial screen of 7 HCAII variants with alanine substitutions in positions 121, 143 and 198, detailed kinetic measurements were performed on HCAII and the variants V121A, V143A and V121A/V143A. For some variants, an increased size of the hydrophobic pocket resulted in increased activities and specificities for longer substrates. For V121A/V143A, the rate of hydrolysis for paranitrophenyl valerate was increased by a factor of approximately 3000. The specificities also changed dramatically, for example V121A/V143A is 6.3 times more efficient with paranitrophenyl valerate than paranitrophenyl acetate, while HCAII is >500 times more efficient with paranitrophenyl acetate than paranitrophenyl valerate. An automated docking procedure was performed on these variants with transition state analogues (TSAs) for the hydrolysis reaction. It was possible to correlate the catalytic rate constants to the docking results, i.e. for each variant, efficient hydrolysis was generally correlated to successful TSA-docking. The observations in this paper show that the redesign increased the catalytic rates for substrates with long acyl chains by removal of steric hinders and addition of new favourable binding interactions.

Evaluation of Solution Oxygenation Requirements for Azonitrile-Based Oxidative Forced Degradation Studies of Pharmaceutical Compounds

AIBN and ACVA oxidative forced degradation models are examined for two drug molecules whose predominant oxidation chemistries arise from different reaction mechanisms (i.e., free radical vs. nucleophilic). Stress was conducted under a variety of initiator concentrations, and under ambient and pressurized oxygen atmospheres. In each case examined, the azonitrile initiator solutions served as a good predictive model of the major oxidative degradation products observed in pharmaceutical formulations. At low to moderate inititator concentrations, the degradation product distributions and degree of reactivity were similar for samples stored in ambient and pressurized oxygen environments. These results are rationalized with reference to the oxygen consumption kinetics of AIBN and ACVA solutions as a function of initiator concentration. The data suggests that ambient air provides sufficient oxygen to enable chain propagation of peroxy radicals in azonitrile solutions of concentrations appropriate to the forced degradation of pharmaceutical compounds.

Interaction of the Indole Class of Vacuolar H+-ATPase Inhibitors with Lipid Bilayers

The selective inhibitor of osteoclastic V-ATPase (2Z,4E)-5-(5,6-dichloro-2-indolyl)-2-methoxy-N-(1,2,2,6,6-pentamethylpiperidin-4-yl)-2,4-pentadienamide (SB 242784), member of the indole class of V-ATPase inhibitors, is expected to target the membrane-bound domain of the enzyme. A structural study of the interaction of this inhibitor with the lipidic environment is an essential step in the understanding of the mechanism of inhibition. In this work, a comprehensive study of the relevant features of this interaction was performed. Inhibitor partition coefficients to lipid vesicles as well as its transverse location, orientation (order parameters), and dynamics while bound to bilayers were determined through photophysical techniques, taking advantage of the intrinsic fluorescence of the molecule. To better evaluate the functionally relevant features of SB 242784, a second inhibitor, INH-1, from the same class and having a reduced activity was also examined. It is shown that regarding membrane interaction their properties remain very similar for both molecules, suggesting that the differences in inhibition efficiencies are solely a consequence of the molecular recognition processes within the inhibition site in the V-ATPase.

Self-Assembly of Precursors in Single-Crystal Growth of Biopolymers

Self-assembly of precursors in dilute solution single-crystal growth of poly[(R)-3-hydroxyvalerate] (PHV) and the fungal polysaccharide mycodextran were studied by transmission electron microscopy, especially at the early stages of crystallization. Precursors for PHV, such as small primary nuclei and tiny square tiles, consolidate to a large square crystal composed of orthogonally arranged tiles. By contrast, the precursors of mycodextran were lath-shaped, which suggests that the crystal growth is mainly in the longitudinal direction. Needlelike precursors were observed either free or as protrusions at the lath ends. In general, single-crystal shape and morphology are dependent on the type of precursor and on the manner of crystallization.