Synthesis of glycosides in which the aglycon is an N-(Hydroxymethyl)amino-1,3,5-triazine derivative

The synthesis of analogues of the anti-tumour drug 2-[N-(hydroxymethyl)methylamino]-4,6-bis (dimethylamino)-1,3,5-triazine (HMPMM) in which the OH or a dimethylamino group is replaced by a carbohydrate has been explored. Triazinyl β-glycosides were readily prepared by reaction of sugars with trimethyl-triazinylammonium salts. These were made with one or two methylamino groups on the triazine for reaction with formaldehyde to give the cytotoxic NMeCH2OH group. However, reaction of the triazinyl glycosides with formaldehyde gave complex intractable mixtures. When the carbohydrate portion was changed to the fully protected 2,3,4,6-tetra-O-acetyl glucose a good yield of the 2-[N-(hydroxymethyl)methylamino]-4-(dimethylamino)-1,3,5-triazin-2-yl tetra-O-acetyl β-glucoside was obtained. However, de-acetylation using sodium methoxide also removed the N–CH2OH group. We are investigating protection of the base-sensitive N–CH2OH group as trialkylsilyl and benzyl ethers and are looking at de-acetylation methods that are more selective. We have prepared glycosides in which the sugar is joined through the oxygen of the NMeCH2OH group. Coupling of acetobromoglucose with HMPMM catalysed by silver salts was not successful. Although methyl and cyclohexyl derivatives of HMPMM may be produced in high yields by reaction of HMPMM with methyl and cyclohexyl alcohols under acidic catalysis, production of glycosides in this way gave poor yields. MNDO calculations on reactions of HMPMM helped us devise improved reaction conditions for the condensation of 2,3,4,6-tetra-O-acetyl glucose with HMPMM and its derivatives. The best procedure to generate one of the target glycosides is to react 2,3,4,6-tetra-O-acetyl glucose and formaldehyde with 2-methylamino- 4,6-bis(dimethylamino)-1,3,5-triazine. The β-glycoside product was de-acetylated using potassium carbonate in dry methanol. Abbreviations: HMM, hexamethylmelamine (2) or 2,4,6-tris(dimethylamino)-1,3,5-triazine; HMPMM, hydroxymethylpentamethylmelamine or 2-[N-(hydroxymethyl)-methylamino]-4,6-bis(dimethylamino)-1,3,5-triazine; PMM, Pentamethylmelamine or 2-methylamino-4,6-bis(dimethylamino)-1,3,5-triazine; TBMS, t-Butyldimethylsilyl; p-TSA, p-Toluenesulphonic acid This revised version was published online in November 2006 with corrections to the Cover Date.     

Characterization of alpha-synuclein interactions with selected aggregation-inhibiting small molecules

The 140-residue protein alpha-synuclein (aS) has been implicated in the molecular chain of events leading to Parkinson's disease, which relates to the hierarchical aggregation of aS into soluble oligomers and insoluble fibrils. A number of small organic molecules have been reported to inhibit aS aggregation. Here, the interactions of chlorazole black E, Congo red, lacmoid, PcTS-Cu (2+), and rosmarinic acid with aS are examined by NMR spectroscopy to identify aS sequence elements that are masked by these compounds. Surprisingly, similar aS interaction sites, encompassing residues 3-18 and 38-51, were obtained for all molecules at equimolar small molecule:aS ratios. At higher ratios, virtually the entire amphiphilic region of aS (residues 2-92) is affected, revealing the presence of additional, lower affinity interaction sites. Upon rearranging the high-affinity interaction sites over the aS amphiphilic region in an aS mutant form, perturbations of the entire amphiphilic region were found to have already been obtained at equimolar ratios, indicating a high specificity for the original binding sites. CD spectroscopy reveals that, in the presence of the small molecules, the aS structure is still dominated by random-coil characteristics. The strongest effects are exerted by molecules that contain sulfonate groups adjacent to aromatic systems, often present in multiple copies in a symmetrical arrangement, suggesting that these elements are useful for developing an aS-specific chemical chaperone.     

Recombinant exochitinase of the thermophilic mould Myceliopthora thermophila BJA: Characteristics and utility in generating N‐acetyl glucosamine and in biocontrol of phytopathogenic fungi

Chitinase from the thermophilic mould Myceliopthora thermophila BJA (MtChit) is an acid tolerant, thermostable and organic solvent stable biocatalyst which does not require any metal ions for its activity. To produce high enzyme titres, reduce fermentation time and overcome the need for induction, this enzyme has been heterologously expressed under GAP promoter in the GRAS yeast, Pichia pastoris. The production medium supplemented with the permeabilizing agent Tween‐20 supported two‐fold higher rMtChit production (5.5 × 10³ U L^?1). The consensus sequences S(132)xG(133)G(134) and D(168)xxD(171)xD(173)xE(175) in the enzyme have been found to represent the substrate binding and catalytic sites, respectively. The rMtChit, purified to homogeneity by a two‐step purification strategy, is a monomeric glycoprotein of ～48 kDa, which is optimally active at 55°C and pH 5.0. The enzyme is thermostable with t_1/2 values of 113 and 48 min at 65 and 75°C, respectively. Kinetic parameters K_m, V_max, k_cat, and k_cat/K_m of the enzyme are 4.655 mg mL^?1, 34.246 nmol mg^?1 s^?1, 3.425 × 10⁶ min^?1, and 1.36 × 10^?6 mg mL^?1 min^?1, respectively. rMtChit is an unique exochitinase, since its action on chitin liberates N‐acetylglucosamine NAG. The enzyme inhibits the growth of phytopathogenic fungi like Fusarium oxysporum and Curvularia lunata, therefore, this finds application as biofungicide at high temperatures during summer in tropics. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:70–80, 2017     

Genetic structure of four socio-culturally diversified caste populations of southwest India and their affinity with related Indian and global groups

Background  

A large number of microsatellites have been extensively used to comprehend the genetic diversity of different global groups. This paper entails polymorphism at 15 STR in four predominant and endogamous populations representing Karnataka, located on the southwest coast of India. The populations residing in this region are believed to have received gene flow from south Indian populations and world migrants, hence, we carried out a detailed study on populations inhabiting this region to understand their genetic structure, diversity related to geography and linguistic affiliation and relatedness to other Indian and global migrant populations.     

Time course of vasodilation at the onset of repetitive skeletal muscle contractions

To characterize the vasodilatory response in the transition from a single skeletal contraction to a series of contractions, we measured the response of hamster cremaster muscle arterioles associated with four to five skeletal muscle fibers stimulated to contract for one, two, three, or four contractions (250-ms train duration) at 4-s intervals [15 contractions per minute (CPM)] for up to 12 s, at stimulus frequencies of 4, 10, 20, 30, 40, 60, and 80 Hz. To investigate the contribution of contraction frequency, we stimulated muscle fiber bundles at 30 or 60 CPM for 12 s at stimulus frequencies of 4, 20, and 60 Hz. Arteriolar diameters at the site of overlap with the stimulated muscle fibers were measured before and after each contraction. At 15 CPM at 4, 20, and 60 Hz, we observed a peak change in diameter following the first contraction of 1.1 +/- 0.1, 1.6 +/- 0.2, and 2.1 +/- 0.2 mum that almost doubled in response to the second contraction (2.0 +/- 0.1, 3.0 +/- 0.1, and 3.8 +/- 0.1 mum, respectively), but there was no further dilation following the third or fourth contraction. A similar response occurred at all stimulus and contraction frequencies tested. At 30 and 60 CPM at 60 Hz, the plateau after two contractions was followed by a further increase in diameter to a second plateau at 7-8 s. Therefore, the vasodilatory response in the transition from single to multiple contractions had components that were stimulation parameter dependent and independent and showed a plateauing behavior indicative of rapid changes in either the nature and/or concentration of vasodilators released or changes in vascular reactivity.     

Development of a model for the δ-opioid receptor pharmacophore. 4. Residue 3 dehydrophenylalanine analogues of Tyr-c[D-Cys-Phe-D-Pen]OH (JOM-13) confirm required gauche orientation of aromatic side chain

We have previously proposed a model for the δ-opioid receptor binding conformation of the high affinity tetrapeptide Tyr-c[D -Cys-Phe-D -Pen] OH (JOM-13) based on experimental and theoretical conformational analysis of this peptide and a correlation of conformational preferences of further conformationally restricted analogues of this tetrapeptide with their receptor binding affinities. A key element of this model is the requirement that the Phe³ side chain exist in the x¹ = −60° conformation. Conformational calculations on the residue 3 dehydrophenylalanine analogues of JOM-13 suggest that while the dehydro(Z) phenylalanine analogue can be superimposed easily with the proposed binding conformer of JOM-13, the dehydro(E)phenylalanine analogue cannot. These results lead to the prediction that the dehydro(Z)-phenylalanine analogue should display similar δ-receptor binding affinity as JOM-13 while the dehydro(E)phenylalanine analogue is expected to bind less avidly. Synthesis and subsequent opioid receptor binding analysis of the dehydrophenylalanine analogues of JOM-13 confirm these predictions, lending support to the δ-pharmacophore model. © 1996 John Wiley & Sons, Inc.     

Biotechnology and bioremediation: successes and limitations

With advances in biotechnology, bioremediation has become one of the most rapidly developing fields of environmental restoration, utilizing microorganisms to reduce the concentration and toxicity of various chemical pollutants, such as petroleum hydrocarbons, polycyclic aromatic hydrocarbons, polychlorinated biphenyls, phthalate esters, nitroaromatic compounds, industrial solvents, pesticides and metals. A number of bioremediation strategies have been developed to treat contaminated wastes and sites. Selecting the most appropriate strategy to treat a specific site can be guided by considering three basic principles: the amenability of the pollutant to biological transformation to less toxic products (biochemistry), the accessibility of the contaminant to microorganisms (bioavailability) and the opportunity for optimization of biological activity (bioactivity). Recent advances in the molecular genetics of biodegradation and studies on enzyme-tailoring and DNA-shuffling are discussed in this paper.