Lactic Acid Residue Research Articles

Sulfated Aeruginosins from Lake Kinneret: Microcystis Bloom, Isolation, Structure Elucidation, and Biological Activity.

Aeruginosins are common metabolites of cyanobacteria. In the course of re-isolation of the known aeruginosins KT608A and KT608B for bioassay studies, we isolated three new sulfated aeruginosins, named aeruginosins KT688 (1), KT718 (2), and KT575 (3), from the extract of a Microcystis cell mass collected during the 2016 spring bloom event in Lake Kinneret, Israel. The structures of the new compounds were established on the basis of analyses of the 1D and 2D NMR, as well as HRESIMS data. Marfey's method, coupled with HR ESI LCMS and chiral HPLC, was used to establish the absolute configuration of the amino acid and hydroxyphenyl lactic acid residues, respectively. Compounds 1-3 were tested for inhibition of the serine protease trypsin, and compounds 1 and 2 were found to exhibit IC50 values of 2.38 and 1.43 µM, respectively.

The Chicken Slaughterhouse in Jember City, Mapping the flesh Total Plate Count, pH, Lactic Acid, and Tetracycline Antibiotics of The Chicken

TThe study's objective was to map the total plate count (TPC), pH, lactic acid, and antibiotic residues, including tetracycline, in broiler meat from the Patrang sub-district in the Jember district. The study employed a descriptive case study methodology and employed ANOVA and the BNT test for data analysis. Significant effects on lactic acid, pH, and microbiological parameters were discovered by the research. Three conventional RPAs did not contain any traces of the antibiotic tetracycline. The investigation came to the conclusion that SNI guidelines and Standard Operating Procedures (SOP) for chicken slaughter were met by the level of antibiotics, lactic acid, pH, TPC, and tetracycline in RPA in Jember City's Patrang environment.

Computational and NMR Conformational Analysis of Galactofuranoside Cycles Presented in Bacterial and Fungal Polysaccharide Antigens.

Unlike pyranoside cycles which are generally characterized by strictly defined conformational preferences, furanosides are flexible and may adopt a wide range of available conformations. During our previous studies, conformational changes of galactofuranoside cycles upon total sulfation were described computationally, using a simple Hartree–Fock (HF) method, and principal conformers of the 5-membered galactose ring were revealed. However, in the case of more complex disaccharide structures, it was found that this method and the widely applied DFT-B3LYP produced results that deviated from experimental evidence. In this study, other DFT functionals (PBE0 and double hybrid B2PLYP) along with RI-MP2 are employed to study the conformational behavior of the galactofuranoside ring. Reinvestigation of galactofuranosides with a lactic acid substituent at O-3 revealed that changes in the orientation of lactic acid residue at O-3 might induce conformational changes of the furanoside cycle. Such findings are important for further modeling of carbohydrate–protein interaction.

Molecular packing handedness dominated by the chirality of the lactic acid residue near the liquid crystalline core

ABSTRACT Eight dichiral compounds containing two lactic acid residues and one perfluorocarbon chain are synthesised. Six of them are liquid crystals with an enantiotropic SmA phase. Two of them are liquid crystals with enantiotropic SmA and SmC* phases. Although (R,R)-3 and (R,R)-4 molecules pack in monolayer structures at the crystalline states, (S,R)-3 and (R,S)-4 molecules pack in bilayer structures at the crystalline states. The optical activity of these compounds is mainly controlled by the chirality of the lactic acid residue near the liquid crystalline core. The dichiral compounds can self-assemble into nanotubes or twisted nanoribbons in methanol. Circular dichroism characterisation indicated that the stacking handedness of the liquid crystalline cores in the organic self-assemblies was also dominated by the chirality of the lactic acid residue near the liquid crystalline core.

Structure and in vitro Bioactivity against Cancer Cells of the Capsular Polysaccharide from the Marine Bacterium Psychrobacter marincola.

Psychrobacter marincola KMM 277T is a psychrophilic Gram-negative bacterium that has been isolated from the internal tissues of an ascidian Polysyncraton sp. Here, we report the structure of the capsular polysaccharide from P. marincola KMM 277T and its effect on the viability and colony formation of human acute promyelocytic leukemia HL-60 cells. The polymer was purified by several separation methods, including ultracentrifugation and chromatographic procedures, and the structure was elucidated by means of chemical analysis, 1-D, and 2-D NMR spectroscopy techniques. It was found that the polysaccharide consists of branched hexasaccharide repeating units containing two 2-N-acetyl-2-deoxy-d-galacturonic acids, and one of each of 2-N-acetyl-2-deoxy-d-glucose, d-glucose, d-ribose, and 7-N-acetylamino-3,5,7,9-tetradeoxy-5-N-[(R)-2-hydroxypropanoylamino]- l-glycero-l-manno-non-2-ulosonic acid. To our knowledge, this is the first finding a pseudaminic acid decorated with lactic acid residue in polysaccharides. The biological analysis showed that the capsular polysaccharide significantly reduced the viability and colony formation of HL-60 cells. Taken together, our data indicate that the capsular polysaccharide from P. marincola KMM 277T is a promising substance for the study of its antitumor properties and the mechanism of action in the future.

Structural and serological characterization of the O82 antigen of a Proteus mirabilis strain isolated from a patient in Poland

P. mirabilis strains Kro 45 and Kwy 46 were isolated from the pus and the muscular fluid, respectively, of a hospitalized 61-year-old female in Łódź, Poland. Both strains demonstrated a good swarming ability on a solid medium, and the Dienes test for differentiation of swarming strains indicated their identity. The strains were serologically identical and did not belong to any of the known Proteus O1-O81 serogroups. In this work, we studied the O-specific polysaccharide (O antigen) of P. mirabilis Kwy46, which defines the immunospecificity of the strain. The O-polysaccharide was obtained by mild acid degradation of the lipopolysaccharide, and the following structure of its oligosaccharide repeat (O-unit) was established by sugar analysis along with 1D and 2D 1H and 13C NMR spectroscopy: [Display omitted] where (S)-lac indicates an (S)-1-carboxyethyl group [an (S)-lactic acid residue], which forms an ether with a GlcNAc residue (so called glycolactilic acid). This structure is unique among Proteus O-polysaccharides but shares a trisaccharide fragment with that of P. mirabilis O5. Studies of the cross-reactivity between P. mirabilis Kwy 46 O antiserum/lipopolysaccharide and Proteus O1-O81 lipopolysaccharides/O antisera allowed identification of a putative Kwy 46 O-antigen epitope. Based on the data obtained, it is proposed to create a new O82 serogroup within the genus Proteus represented by the studied P. mirabilis isolates.

Chirality driven mesomorphic behaviour difference: dichiral compounds containing two lactate groups

ABSTRACTFour compounds containing two lactate groups and one perfluorocarbon chain are designed and synthesised, whose chirality is tuned by changing the chirality of the lactic acid residues. (R,S)- and (S,R)-2 stereoiosomers exhibit an enantiotropic SmA phase, while (R,R)- and (S,S)-2 stereoisomers exhibit an enantiotropic SmA phase and an enantiotropic SmCd* one. Therefore, the chirality of the compounds plays an important role in the mesomorphic behaviours of the compounds. The optical activity of these liquid crystals is dominated by the chirality of the lactate group near the core. (R)- and (S)-1 with one lactic acid residue and one perfluorocarbon chain exhibit only an enantiotropic SmA phase.

Structure of the LPS O-chain from Fusobacterium nucleatum strain MJR 7757 B

Fusobacterium nucleatum is an anaerobic bacterium found in the human mouth where it causes periodontitis. It was also found in colorectal cancer tissues and is linked with pregnancy complications, including pre-term and still births. Cell surface structures of the bacterium could be implicated in pathogenesis. Here we report the following structure of the lipopolysaccharide O-chain of F. nucleatum strain MJR 7757 B:where Lac is (R)-1-carboxyethyl (lactic acid residue); all monosaccharides are in the pyranose form. ManNAc4Lac, analogue of N-acetylmuramic acid, is found for the first time in natural sources.

Definitive structural assessment of enterococcal diheteroglycan.

Enterococcus faecalis is one of most important nosocomial and often multi-antibiotic resistant pathogens responsible for infections that are difficult to treat. Previously, a cell-wall polysaccharide termed diheteroglycan (DHG) was isolated and characterized as a promising vaccine candidate. However, the configuration of its lactic acid (LA) residue attached to the galactofuranoside unit was not assessed, although it influences conformation of DHG chain in terms of biological recognition and immune evasion. This study proves the R configuration of the LA residue by means of chemical analysis, investigation of intramolecular NMR nuclear Overhauser effects and molecular dynamics simulations of native DHG and corresponding R and S models, which were obtained by using pyranoside-into-furanoside rearrangement. As alternative treatment and prevention strategies for E. faecalis are desperately needed, this discovery may offer the prospect of a synthetic vaccine to actively immunize patients at risk.

Redox Behaviour of Verbascoside and Rosmarinic Acid

The electrochemical oxidation mechanisms of rosmarinic acid (RA) and verbascoside (VB), both caffeic acid esters with two catechol moieties, were investigated. The redox mechanism is associated with the oxidation of the catechol groups, and was studied over a wide pH range by cyclic, differential pulse and square wave voltammetry, using a glassy carbon electrode. The voltammetric study revealed that both molecules, RA and VB, are reversibly oxidized in two successive pH-dependent steps each with the transfer of two electrons and two protons. Moreover, it was found that the first oxidation step is associated with the caffeic acid moiety, whereas the second oxidation step corresponds to the oxidation in VB of the hydroxytyrosol group and in RA of the 3,4-dihydroxyphenyl lactic acid residue.

Synthesis and photoresponsive behavior of optically active methacrylic homopolymers containing side-chain spiropyran chromophores

Abstract Novel optically-active methacrylic homopolymers bearing in the side chain one or more chiral groups of one single configuration (based on the l -lactic acid residue) linked to the spiropyran chromophore, have been successfully synthesized and fully characterized. These intrinsically chiral polymers exhibit remarkable thermal stability, with glass transition temperatures in the range 100–130 °C and decomposition temperatures around 270 °C. The chiroptical characterization indicates the occurrence of asymmetric induction on the electronic transitions of the side-chain chromophore related to the number of l -lactic acid residues interposed between the main chain and the spiropyran chromophore. In the presence of acid, these systems can be used to modulate the protonation of polymeric azopyridine moieties upon photoisomerization of the spiropyran group. In addition to UV–Vis spectroscopy, the proton transfer process occurring between the macromolecular components can be also followed by CD spectroscopy, the system thus behaving as a chiroptical switch.

Identification of Three Novel Polyphenolic Compounds, Origanine A–C, with Unique Skeleton from Origanum vulgare L. Using the Hyphenated LC-DAD-SPE-NMR/MS Methods

Identification of new compounds especially those with new skeletons from plant kingdom has long been a vital aspect for understanding phytochemistry, plant metabolisms and discovering new bioactive compounds. In this study, we identified and isolated three novel polyphenolic compounds, origanine A-C, from a well-researched plant Origanum vulgare L. using the hyphenated LC-DAD-SPE-NMR/MS methods. Based on the combined information from UV-visible, accurate mass and 2D NMR spectra together with computational calculations, we found that these compounds all had a novel skeleton of cyclohexenetetracarboxylic acids attached with some well-known bioactive moieties including 3,4-dihydroxyphenyl, 4-(β-d-glucopyranosyloxy)benzyl alcohol (gastrodin), and 3-(3,4-dihydroxyphenyl)lactic acid (danshensu) residues. These findings provided crucial information to fill the gaps in our knowledge in terms of the plant secondary metabolism. This study also indicated the necessity for further research in plant secondary metabolism for even well-studied plants and demonstrated the powerfulness of the hyphenated LC-DAD-SPE-NMR/MS methods for comprehensive analysis of plant metabolites in particular for discovering new natural compounds.

Conformational Preferences and Cis−Trans Isomerization of l-Lactic Acid Residue

The conformational study on N-acetyl- N'-methylamide of l-lactic acid (Ac-Lac-NHMe, the Lac dipeptide) is carried out using ab initio HF and density functional methods with the self-consistent reaction field method to explore its backbone conformational preferences and cis-trans isomerization for the depsipeptide with an ester bond in the gas phase and in solution. In the gas phase and in chloroform, the conformation tB with a trans depsipeptide bond is most preferred for the Lac dipeptide, whose backbone torsion angles are phi approximately -150 degrees and psi approximately -5 degrees , juxtaposed to those of the 3 10-helical structure. The larger shift in phi is brought to reduce the repulsion between the two carbonyl carbons of the acetyl and NHMe groups. However, the polyproline II-like tF conformation becomes more populated and the relative stability of conformation tB decreases significantly as the solvent polarity increases. This may be ascribed to weakening a C(5) hydrogen bond between the depsipeptidyl oxygen and the carboxyl amide hydrogen that plays a role in stabilizing the conformation tB in the gas phase and in chloroform. The cis populations about the depsipeptide bond are nearly negligible in the gas phase and in solution. The rotational barriers to the cis-trans isomerization of the depsipeptide bond for the Lac dipeptide are calculated to be about 11 kcal/mol, which is about half of those for the Ala dipeptide, although they increase somewhat with the increase of solvent polarity. The cis-trans isomerization of the depsipeptide bond proceeds through either clockwise or anticlockwise rotations with torsion angles of about +90 degrees or -90 degrees , respectively, in the gas phase and in solution, whereas it has been known that the isomerization proceeds through only the clockwise rotation for alanyl and prolyl peptide bonds. The pertinent distances between the depsipeptidyl oxygen and the carboxyl amide hydrogen can describe the role of this hydrogen bond in stabilizing the transition state structures in the gas phase and in solution.

Synthesis of fluorescent-labeled aeruginosin derivatives for high-throughput fluorescence correlation spectroscopy assays

The design and solid-phase synthesis of effective fluorescent-labeled aeruginosin derivatives and their application to the fluorescence correlation spectroscopy (FCS)-based competitive binding assay of an aeruginosin library are described. The phenolic hydroxyl group on the ( R)-3-(4-hydroxyphenyl)lactic acid ( d-Hpla) residue was observed to be suitable for connecting Rhodamine green derivative with minimum loss of biological activity. In addition, the FCS-based binding assay of the library using fluorescent-labeled chemical probes was also achieved.

Symmetrical biodegradable crosslinkers for use in polymeric devices

There is a need for biodegradable hydrogels that deteriorate at defined rates under physiological conditions for use in engineered tissue constructs and drug delivery. These hydrogels should contain components that are readily synthesized, biocompatible and easily incorporated into hydrogel networks. This need was addressed through a judiciously designed series of crosslinkers composed of symmetrical oligo-glycolate and oligo-lactate esters terminated with vinylic moieties ( 1 ). These materials were incorporated into poly(HPMA) networks via free-radical polymerization. This work describes the preparation of symmetrical, lactate and glycolate ester based crosslinking agents and their incorporation into a hydrogel network composed of 2-hydroxypropyl methacrylamide (HPMA). By varying the number of lactic and glycolic acid residues ( n = 0, 1, 2) within the crosslinker, the rate of hydrolytic degradation of the gel can be controlled.

13C NMR chemical shifts of the triclinic and monoclinic crystal forms of valinomycin.

Two different crystalline polymorphs of valinomycin, the triclinic and monoclinic forms, have been studied by high resolution, solid state (13)C CP-MAS NMR spectroscopy. Although the two polymorphs of the crystal are remarkably similar, there are distinct differences in the isotropic chemical shifts between the two spectra. For the triclinic form, the carbon chemical shift tensor components for the alpha carbons adjacent to oxygen in the lactic acid and hydroxyisovaleric acid residues and the ester carbonyls of the valine residue were obtained using the FIREMAT experiment. From the measured components, it was found that the behavior of the isotropic chemical shift, delta(iso), for valine residue ester carbonyl carbons is predominately influenced by the intermediate component, delta(22). Additionally it was found that the smallest shift component, delta(33), for the L -lactic acid ( L -Lac) and D -alpha-hydroxyisovaleric acid ( D -Hyi) C(alpha)-O carbon was significantly displaced depending upon the nature of individual amino acid residues, and it is the delta(33) component that governs the behavior of delta(iso) in these alpha carbons.

Restricted conformation analogues of an anthelmintic cyclodepsipeptide.

Six analogues of the anthelmintic cyclodepsipeptide PF1022A were prepared, each containing a small ring fused to the macrocycle to restrict the number of conformations the larger ring can adopt. It was anticipated that such conformational changes could lead to enhanced biological activity and selectivity. The analogues form two series of three members each. In one series, a carbon-based molecular bridge joins the methyl of a leucine residue with the methyl of its closest lactic acid residue to form five-, six-, and seven-membered lactam rings. In the second series, a leucine residue is replaced with five-, six-, and seven-membered nitrogen heterocycles. Decreasing the size of the small ring in the lactam series increasingly distorts the macrocycle and consistently decreases activity relative to PF1022A. In the leucine series, a similar trend is observed. Molecular modeling of PF1022A along with the analogues described herein suggests that the ability to exist in a highly symmetrical conformational state is a necessary condition for biological activity.

Self-assembling biomaterials: Liquid crystal phases of cholesteryl oligo(l-lactic acid) and their interactions with cells

We report here on the synthesis and characterization of a series of self-assembling biomaterials with molecular features designed to interact with cells and scaffolds for tissue regeneration. The molecules of these materials contain cholesteryl moieties, which have universal affinity for cell membranes, and short chains of lactic acid, a common component of biodegradable tissue engineering matrices. The materials were synthesized in good yields with low polydispersities in the range of 1.05-1.15, and their characterization was carried out by small-angle x-ray diffraction, transmission electron microscopy, electron diffraction, differential scanning calorimetry, and atomic force microscopy. These molecular materials form layered structures that can be described as smectic phases and can also order into single-crystal stacks with an orthorhombic unit cell. Their layer spacings range from 58 to 99 A, corresponding to bilayers of oligomers with an average of 10 and 37 lactic acid residues, respectively. The self-organized layered structures were found to promote improved fibroblast adhesion and spreading, although the specific mechanism for this observed response remains unknown. The ability of self-assembling materials to present ordered and periodic bulk structures to cells could be a useful strategy in tissue engineering.

Structural analysis of peptide helices containing centrally positioned lactic acid residues.

The effect of insertion of lactic acid (Lac) residues into peptide helices has been probed using specifically designed sequences. The crystal structures of 11-residue and 14-residue depsipeptides Boc-Val-Val-Ala-Leu-Val-Lac-Leu-Aib-Val-Ala-Leu-OMe (1) and Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-Val-Lac-Leu-Aib-Val-Ala-Leu-OMe (3), containing centrally positioned Lac residues, have been determined. The structure of an 11-residue peptide Boc-Val-Ala-Leu-Aib-Val-Ala-Leu-Aib-Val-Ala-Leu-OMe (2), analog of a which is an amide previously determined Lac-containing depsipeptide, Boc-Val-Ala-Leu-Aib-Val-Lac-Leu-Aib-Val-Ala-Leu-OMe I. L. Karle, C. Das, and P. Balaram, Biopolymers, Vol. 59, (2001) pp. 276-289], is also reported. Peptide 1 adopts a helical fold, which is stabilized by mixture of 4-->1 and 5-->1 hydrogen bonds. Peptide 2 adopts a completely alpha-helical conformation stabilized by eight successive 5-->1 hydrogen bonds. Peptide 3 appears to be predominately alpha-helical, with seven 5-->1 hydrogen bonds and three 4-->1 interaction interspersed in the sequence. In the structure of peptide 3 in addition to water molecules in the head-to-tail region, hydration at an internal segment of the helix is also observed. A comparison of five related peptide helices, containing a single Lac residue, reveals that the hydroxy acid can be comfortably accommodated at interior positions in the helix, with the closest C=O...O distances lying between 2.8 and 3.3 A.

Structure of a new N-acetylisomuramic acid-containing O-specific polysaccharide of Proteus penneri strains 19 and 35

O-Specific polysaccharides, together with oligosaccharide products of their degradation, were isolated by GPC after mild acid delipidation of lipopolysaccharides of Proteus penneri strains 19 and 35. The polysaccharides had the same trisaccharide repeating unit containing one residue each of d-galactose, 2-acetamido-2-deoxy- d-glucose, and 2- acetamido-3-O-[(S)-1- carboxyethyl]-2-deoxy- d-glucose ( N-acetylisomuramic acid). On the basis of 1D and 2D 1H and 13C NMR spectroscopy, including 2D correlation spectroscopy (COSY), rotating-frame NOE spectroscopy (ROESY), and H-detected heteronuclear 1H, 13C multiple-quantum coherence (HMQC), the following structure of the repeating unit was established: ▪ The oligosaccharide products formed by cleavage of the glycosidic linkage of GlcNAc represent a chemical trisaccharide repeating unit of the polysaccharide and its oligomer homologs. The ease of hydrolysis of the polysaccharide is associated with the closeness of the glycosyl group and the lactic acid residue in N-acetylisomuramic acid. The polysaccharides studied are structurally related to the O-specific polysaccharides of P. penneri strains 62 and 71 studied by us earlier.