Structure and synthesis of atalaphylline and related alkaloids

The structure of atalaphylline, (1; 1,3,5-trihydroxy-4-(γ,γ-dimethylallyl)acridone an alkaloid of Atalantia monophylla, was confirmed by oxidative degradation and by total synthesis. The synthesis involved the preparation of 1,3,5-trihydroxy-9-acridone followed by direct prenylation to give atalaphylline and a monoprenylated product.     

The effect of granulocyte colony stimulating factor receptor gene missense single nucleotide polymorphisms on peripheral blood stem cell enrichment

Granulocyte-colony stimulating factor (G-CSF) has become the most effective agent supporting hematopoietic stem cell transplantation (HSCT). The cognate interaction between G-CSF and its specific receptor, G-CSFR, induces the mobilization of HSCs and increases their pool in the peripheral blood. G-CSFR has a highly conserved structure which may be functionally modulated by the presence of missense single nucleotide polymorphisms (SNPs). In this study, we asked whether the missense SNPs in G-CSFR could affect the response to G-CSF in HSCT patients and donors. Here, for the first time, G-CSFR missense SNPs were screened and minor allele frequencies were determined in a specific population with Turkish racial background. Five (rs3917991, rs3918001, rs3918018, rs3918019, and rs146617729) out of 16 missense SNPs screened were determined with minor allele frequencies lower than 0.04. Subsequent association analyses indicated potential impact of rs3918001, rs3918018, and rs3918019 minor alleles on peripheral blood CD34⁺ cell enrichment. Although their frequency is rather low, certain missense SNPs, especially which are placed in the conserved regions of G-CSFR may possess the capacity to influence the response to G-CSF treatment.     

Immunocytochemical localization of H+?K+-ATPase in the rat colon

Summary The presence and distribution of gastric-type H⁺−K⁺-ATPase were investigated in the rat colon using a monoclonal antibody raised against hog gastric H⁺−K⁺-ATPase. Rat stomach was used as positive control. Rat kidney and ileum, in both of which H⁺−K⁺-ATPase has been reported in the past, were also studied. In stomach, very strong staining was found confined to the parietal cells, and a strong band atM _r∼94 kDa on the immunoblots. In colon a moderate staining was found in the supranuclear region of the epithelial cells, with similar intensity and distribution of staining of the surface and deep mucosa of the crypts, throughout the length of the colon. Another monoclonal antibody, specific to the 31 kDa subunit of H⁺-ATPase, used as a negative control, or omission of the primary antibody, resulted in lack of any staining in either colon or stomach. On immunoblots of homogenates of colonic mucosa, no specific band could be identified, either due to very low expression of the H⁺−K⁺-ATPase or loss of antigenicity of the epitope during the processing steps. No positive staining was observed in rat kidney and ileum, suggesting that they contain isoforms that are structurally different.     

Detection of Aflatoxin in Aspergillus Species Isolated from Pistachio in Iran

To estimate the incidence contamination of fresh pistachio nuts by aflatoxigenic fungi in Iran, nut samples were collected from pistachio orchards in Kerman, Rafsanjan and Isfahan regions. Out of the 200 Aspergillus isolates obtained, 11 species were identified as A. alliaceous, A. candidus, A. flavus, A. niger, A. niveus, A. ochraceus, A. parasiticus, A. tamari, A. terreus, A. unguis and A. wentii. For detection of aflatoxin production ability of the isolates, three target genes, namely aflR, aflJ, and omtB, used in PCR amplification. In all the examined cases, the degenerate primer designed for amplification of omtB gene, named omtBII, was able to amplify an expected 611 bp fragment in aflatoxigenic isolates in this study and yielded the same result as those obtained from TLC analysis and fluorescence ability by application of methylated β‐cyclodextrin in culture media. Using this procedure the significant incidence of aflatoxin‐producing aspergilli was confirmed in pistachio nuts produced in different regions of Iran. The results indicated that PCR method described here, in combination with fluorescence assay, is a reliable and simple confirmatory test for monitoring pistachio nuts contaminated with aflatoxinogenic aspergilli.     

Modeling the deamidation of asparagine residues via succinimide intermediates

Density functional theory (B3LYP/6-31G*) has been used to study the cyclization, deamidation and hydrolysis reactions of a model peptide. Single point energy calculations with the polarized continuum model drastically lower the activation energy for cyclization in a basic medium. Confirmation of the experimental results that cyclization is slower than deamidation in acidic media and the opposite is true in basic media has enabled us to propose mechanisms for both processes.     

Vibrational Dynamics of Icosahedrally Symmetric Biomolecular Assemblies Compared with Predictions Based on Continuum Elasticity

Coarse-grained elastic network models elucidate the fluctuation dynamics of proteins around their native conformations. Low-frequency collective motions derived by simplified normal mode analysis are usually involved in biological function, and these motions often possess noteworthy symmetries related to the overall shape of the molecule. Here, insights into these motions and their frequencies are sought by considering continuum models with appropriate symmetry and boundary conditions to approximately represent the true atomistic molecular structure. We solve the elastic wave equations analytically for the case of spherical symmetry, yielding a symmetry-based classification of molecular motions together with explicit predictions for their vibrational frequencies. We address the case of icosahedral symmetry as a perturbation to the spherical case. Applications to lumazine synthase, satellite tobacco mosaic virus, and brome mosaic virus show that the spherical elastic model efficiently provides insights on collective motions that are otherwise obtained by detailed elastic network models. A major utility of the continuum models is the possibility of estimating macroscopic material properties such as the Young's modulus or Poisson's ratio for different types of viruses.