Structure and Conformation of 1-β-D-Ribo Furanosyl Pyridin-2-one-5-Carboxamide: An Anti-Inflammatory Agent

The pyrimidine nucleoside, 1-β-D-ribofuranosyl pyridine-2-one-5-carboxamide, is an anti inflammatory agent used in the treatment of adjuvant-induced arthritis. It is the 2-one isomer of 1-β-D-ribofuranosyl pyridine-4-one 5-carboxamide, an unusual nucleoside isolated from the urine of patients with chronic myelogenic leukemia and an important cancer marker. Crystals of 1-β-D-ribofuranosyl pyridine-2-one-5-carboxamide are monoclinic, space group C2, with the cell dimensions a = 31.7920(13), b = 4.6872 (3), c = 16.1838(11), β = 93.071(3)°, V = 2408.2(2) ų, D_calc = 1.496 mg/m³ and Z = 8 (two molecules in the asymmetric unit). The structure was obtained by the application of direct methods to diffractometric data and refined to a final R value of 0.050 for 1669 reflections with I ≥ 3σ. The nucleoside exhibits an anti conformation across the glycosidic bond (χ_CN = ?15.5°, ?18.9°), a C3 ′- endo C2 ′ -exo [³ ₂T] ribose pucker and g⁺ across the C(4 ′)-C(5 ′) exocyclic bond. The amino group of the carboxamide group is distal from the 2-one and lacks the intramolecular hydrogen bonding found in the related 2-one molecule. Nuclear magnetic resonance studies shows also an anti conformation across the glycosidic bond but the solution conformation of the furanose ring is not the same as that found in the solid state.     

Chemical synthesis of sulfated oligosaccharides with a beta-D-Gal-(1-->3)

The syntheses of two sulfated pentasaccharides: beta-D-Gal6SO3Na-(1-->3)-[beta-D-Gal-(1-->4)-alpha-L-Fuc-(1-->3)-beta-D-Glc-NAc-(1-->6)]-alpha-D-GalNAc-->OMe (1) and beta-D-Gal6SO3Na-(1-->3)-[beta-D-Gal-(1-->4)-alpha-L-Fuc-(1-->3)-beta-D-Glc-NAc6SO3Na-(1-->6)]-alpha-D-GalNAc-->OMe (2) by using Lewisx trisaccharides 12 and 16 as glycosyl donors are described. Sulfated oligosaccharides 1-2 and intermediate compounds are fully characterized by 2D 1H-1H DQF-COSY and 2D ROESY experiments.     

Investigation of human serum albumin (HSA) binding specificity of certain photosensitizers related to pyropheophorbide-a and bacteriopurpurinimide by circular dichroism spectroscopy and its correlation with in vivo photosensitizing efficacy

A series of pyropheophorbide-a and bacteriopurpurinimides were investigated to understand the correlation between HSA (site II) binding affinity and in vivo photosensitizing activity. In our study, photosensitizers that bound to site II of HSA produced a significant difference in the circular dichroism spectra of the corresponding complexes, especially at Soret band region of the photosensitizers. Our results suggest that CD spectroscopy of the photosensitizer-HSA complexes could be a valuable tool in screening new photosensitizers before evaluating them for in vivo efficacy.     

Crystal and molecular structure and absolute configuration of lincomycin hydrochloride monohydrate

Lincomycin is a broad-spectrum antibiotic synthesized by Streptomyces lincolnensis that is particularly active against Gram-positive bacteria. It is widely used in human and veterinary applications. The crystal structure of lincomycin has been undertaken with a view to obtain the conformational and structural features of the drug in order to afford a comparison of its structural features with other aminoglycoside antibiotics. We report here the details of its structural and conformational features as determined by single-crystal X-ray crystallography. Crystals of lincomycin hydrochloride are orthorhombic, space group P2(1)2(1)2, with the cell dimensions a=18.5294(3) Angstroms, b=20.5980(4) Angstroms, c=6.17380(10) Angstroms, V=2356.35(7) Angstroms3. The structure was solved using X-ray diffraction data and refined to a final R-value of 0.0391 for 2321 reflections (I > or = 2sigma). The absolute configuration was established using the anomalous dispersion of the sulfur and chlorine atoms in the structure. The molecule consists of an amino acid linked by an amide group to a monosaccharide of galactose stereochemistry. A network of hydrogen-bonds stabilizes the crystal structure.     

Introduction and expression of genes for metabolic engineering applications in Saccharomyces cerevisiae

Metabolic pathway engineering in the yeast Saccharomyces cerevisiae leads to improved production of a wide range of compounds, ranging from ethanol (from biomass) to natural products such as sesquiterpenes. The introduction of multienzyme pathways requires precise control over the level and timing of expression of the associated genes. Gene number and promoter strength/regulation are two critical control points, and multiple studies have focused on modulating these in yeast. This MiniReview focuses on methods for introducing genes and controlling their copy number and on the many promoters (both constitutive and inducible) that have been successfully employed. The advantages and disadvantages of the methods will be presented, and applications to pathway engineering will be highlighted.     

Burden of Liver Disease among Community-Based People Who Inject Drugs (PWID) in Chennai,India

Background and Objective

We characterize the burden of liver disease in a cohort of PWID in Chennai, India, with a high prevalence of HCV.

Materials and Methods

1,042 PWID were sampled through community outreach in Chennai. Participants underwent fasting blood draw, questionnaire and an examination that included liver stiffness assessment using transient elastography (Fibroscan) and assessment of steatosis via ultrasound.

Results

The median age was 39 years, all were male, 14.8% were HIV infected and 35.6% were HCV antibody positive, of whom 78.9% were chronically infected (HCV RNA positive). Median liver stiffness was 6.2 kPA; 72.9% had no evidence of or mild stiffness, 14.5% had moderate stiffness, and 12.6% had evidence of severe stiffness/cirrhosis. Prevalence of severe stiffness/cirrhosis was significantly higher among persons who were older, had a longer duration of injecting drugs, higher body mass index, higher prevalence of insulin resistance, higher prevalence of steatosis, higher HCV RNA levels and evidence of alcohol dependence. An estimated 42.1% of severe stiffness/cirrhosis in this sample was attributable to HCV. 529 (53.0%) had some evidence of steatosis. Prevalence of steatosis was higher among those who had larger waist circumference, insulin resistance, higher HDL cholesterol and a history of antiretroviral therapy.

Conclusions

We observed a high burden of liver disease in this relatively young cohort that was primarily driven by chronic HCV infection, metabolic factors (insulin resistance and steatosis) and heavy alcohol use. Interventions to improve access to HCV treatment and reduce alcohol use are needed to prevent further progression of liver disease.     

Crystal structure, conformation, and absolute configuration of kanamycin A

Kanamycin, an antibiotic complex produced by Streptomyces kanamycetius isolated from Japanese soil, was described by Okami and Umezawa as early as 1957 and consists of three components: Kanamycin A (the major component), B, and C. The disulfate salt of kanamycin A [4-O-(6-amino-6-deoxy-alpha-d-glucopyranosyl)-6-O-(3-amino-3-deoxy-alpha-d-glucopyranosyl)-2-deoxystreptamine] is a broad-spectrum antibiotic that is used to treat gonorrhea, salmonella, tuberculosis, and many other diseases. Crystals of kanamycin A monosulfate monohydrate obtained from water are triclinic, space group P1, with a=7.2294(14), b=12.4922(15), c=7.1168(9), alpha=94.74(1), beta=89.16(1), gamma=91.59(1), V=640.2(2)A(3), micro(CuKalpha)=18.4cm(-1), FW 600.6, D(calc)=1.558g/cm(3), CAD-4 diffractometric data (2693 reflections, 25543sigma(I)), structure by shelx-86 and refined by full-matrix least squares to a final R value of 0.038. The wrong conformer had an R value of 0.043. Both of the d-glucose moieties are attached to the deoxystreptamine by alpha linkages. This absolute configuration agrees with the earlier determination by both chemical and X-ray methods with photographic data. The (phi,psi) values for the glycosidic linkages are 101.6 degrees , -121.1 degrees , 106.3 degrees , and -140.4 degrees , respectively. Kanamycin interacts with the ribosomal S12 protein to stabilize the codon-anticodon binding between mRNA and the aminoacyl tRNA and inhibits the elongation of peptide chains through a series of reactions resulting in the prevention of ribosomes from moving along mRNA.     

Synthesis,structure, and conformation of anti-tumor agents in the solid and solution states: hydroxyl derivatives of Ftorafur

The pyrimidine antimetabolite Ftorafur [FT; 5-fluoro-1-(tetrahydro-2-furyl)uracil] has shown significant antitumor activity in several adenocarcinomas with a spectrum of activity similar to, but less toxic than, 5-fluorouracil (5-FU). It is considered as a prodrug that acts as a depot form of 5-FU, and hence the two drugs exhibit a similar spectrum of chemotherapeutic activity. Ftorafur is metabolized in animals and humans when hydroxyl groups are introduced into the tetrahydrofuran moiety. These metabolites are also thought to be as active as ftorafur but less toxic than 5-FU. Hydroxyl derivatives: 2'-hydroxyftorafur (III), 3'-hydroxyftorafur (IV) and 2',3'-dihydroxyftorafur (II) were synthesized and X-ray and NMR studies of these hydroxyl derivatives were undertaken in our laboratories to study the structural and conformational features of Ftorafur and its metabolites in the solid and solution states. X-ray crystallographic investigations were carried out with data collected on a CAD-4 diffractometer. The structures were solved and refined using the SDP crystallographic package of Enraf-Nonius on PDP 11/34 and Microvax computers. All of the compounds studied had the base in the anti conformation. The glycosidic torsion angles varied from -20 to 60 degrees. There is an inverse correlation between the glycosyl bond distances and the chi angle. Molecules with a lower chi angle have a larger bond distance and vice versa. The sugar rings show a wide variation of conformations ranging from C2'-endo through C3'-endo to C4'-exo. The crystal structures are stabilized by hydrogen bonds involving the base nitrogen atom N3 and the hydroxyl oxygen atoms of the sugar rings as donors and the keto oxygens O2 and O4 of the base and the hydroxyl oxygen atoms O2' and O3' as acceptors. The NMR studies were carried out on Brüker 400 and 600 MHz instruments. Simulated proton spectra were obtained through Laocoon, and pseudorotational parameters were solved by Pseurot. Presence of syn or anti forms was demonstrated with the use of NOE experiments. The glycosyl conformations in solution vary more widely than in the solid state. The conformations of the sugar molecules are in agreement with the values obtained in the solid state. The studies of the structure and conformation in the solid and solution states give a model for the Ftorafur molecule that could be used in structure, function and biological activity correlation studies.     

Copper binding to prion octarepeat peptides, a combined metal chelate affinity and immunochemical approaches

Based on the hypothetical proposal of Sulkowski [E. Sulkowski, FEBS Lett. 307 (2) (1992) 129] for the implication of transition metal ions in the structural changes/oligomerisation of normal cellular prion protein (PrPc) resulting in the pathological isoform (PrPsc), we focused our study on the octarepat domain of this protein which has been supposed to be the metal binding site. We have studied the copper binding to synthetic prion octarepeat peptides (PHGGGWGQ)n (n=1, 3, 6) using metal chelate and size-exclusion modes of chromatographies. This copper binding induces oligomerisation resulting in multiple aggregates. Moreover, heterogeneity of metal bound octarepeat oligomers by ESI-MS has been demonstrated. In addition, anti prion antibodies specific to the octarepeat region were used to discriminate between metal free and copper, nickel and zinc bound hexamer octarepeat peptide. Differential recognition of Cu(II) and Zn(II) bound complexes has been observed which signify differences in exposed epitopes of aggregated peptides.