Iranian Journal of Biotechnology
Year:2006 | Volume:4 | Issue:1|Papers Count:8

Class-Pi of glutathione s-transferases (GST-Pi) is the specific form of GSTs that are known to participate particularly in the mechanisms of resistance to drugs and carcinogens. This class of the enzyme is referred to as class-P or class-Pi or class π. The accepted terminology in this review article is class-Pi. In this article following a brief description of identified molecular forms of GSTs, we focus on GST-Pi. We review new findings about the structure and regulation of GST-Pi gene. Then, the role of GST-Pi in liver damage, oxidative stress, carcinogenesis and drug resistance are discussed. Also, the presence of common genetic polymorphism, hypermethylation in GST-Pi gene and the consequences GST-Pi knock out is regarded.

In the present study we attempted to correlate the structure and function of the cry11a (72 kDa) and cry4a (135 kDa) proteins of Bacillus thuringiensis var israelensis. Homology modeling and secondary struc ture predictions were done to locate most probable regions for finding helices or strands in these proteins. The JPRED (JPRED consensus secondary structure prediction server) secondary structure predictions were chosen for its ability to predict with high accuracies. The homology model predicted by CPH (CPH Homology Modelling server) modeler showed a distinct region of helices and sheets. The membrane spanning helices were predicted using TOPPRED (TOPPRED Topology prediction of membrane proteins server); these helices are known to play crucial role in cell lyses. The role of one such segment corresponding to amino acids 132-150 of cry4a protein, which had a large hydrophobic moment, was elucidated. The Circular Dichroism spectra of the peptide showed helical structure in methanol and b  sheet structure in HEPES (4-(2- hydroxyethyl) -1-piperazineethanesulfonic acid). The biological activity of this peptide was investigated. The peptide showed weak hemolytic activity in vitro. This may be due to the synthetic peptide used rather than the whole molecule in the native environment. The ability of the peptide and the alkali solubilized crystal proteins to perturb the synthetic membrane was investigated using carboxyflourescein trapped liposomes. The leakage caused by alkali solubilized extract was double than the leakage caused by synthetic peptide. In case of alkali solubilized extract, various osmoprotectants were seen to delay lytic activity. Thus it is clear that the cry proteins are highly active and lethal in their native state. Not only the membrane spanning segments but the whole molecule plays a crucial role in lysis.

The maximum acid phosphatasic activity was detected in peanut seed at the 5th day of germination. At least, two acid phosphatases were purified by successive chromatography separations on DEAE-Sepharose CL-6B, CM-Sepharose CL-6B, Sephacryl S-100 HR, and Phenyl-Sepharose HP to apparent homogeneity from five days old cotyledon of peanut after germination. These isoenzymes, designated peanut cotyledon acid phosphatase 1 and 2 (PCAP 1 and PCAP 2), had native molecular weights of approximately 27.5 and 24 kDa by gel permeation, respectively. SDS-PAGE (Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis) of PCAP 1 and PCAP 2 resolved a single protein band (each) that migrated to approximately 27 and 29 kDa, respectively. Thus, these acid phosphatases likely function as a monomer. The two isoenzymes had a similar optimum temperature (55°C), two closely optima pH (5.6 and 5.0), and appeared to be stable in the presence of some detergents such as Triton X-100, Nonidet P-40, Taurocholic acid sodium salt, Polyoxyethylene-9-lauryl ether as well as Mg2+, Sr2+, Fe3+ and Ba2+. Substrate specificity indicated that PCAP 1 and PCAP 2 hydrolyzed a broad range of phosphorylated substrates. However, natural substrates such as ADP, ATP and phenylphosphate had the highest rate of hydrolysis for the two isoenzymes.

In order to characterize Iranian grape (Vitis vinifera L.) germplasm, 136 genotypes were collected from five grape growing regions (Azarbaijan, Qazvin, Kordestan, Khorasan and Fars) and genotyped along with 36 European cultivars using 9 sequence tagged microsatellite sites (STMS) markers. The used set of markers could distinguish all 172 genotypes under study. Altogether 84 polymorphic alleles were observed detected all the genotypes, with an average of 9.33 and 5.81 effective alleles per locus. The expected heterozygosity values were higher than those observed for all the loci. This could probably be due to the occurrence of null alleles at these loci. The usefulness of this set of markers for genotype distinction was assessed as probability of identity (PI). The estimated total PI value over all the geographic regions for this set of markers was estimated to be 5.67×10-9. Comparison of samples from different grape growing regions of Iran and Europe based on various parameters using allelic data revealed similar level of genetic variation. Analysis of molecular variance (AMOVA) indicated significant difference between samples, however, no difference was observed between the Iranian and European groups. Genetic differentiation among samples based on Fst in most pairwise comparisons was significant. Cluster analysis based on coancestry coefficient matrix and principal coordinate analysis confirmed the result of AMOVA and Fst analysis.

The potential bioconversion of synthesis gas (syngas) to fuels and chemicals by microbial cell has attracted considerable attention in past decade. The feasibility of enhancing syngas bioconversion to ethanol and acetate using Clostridium ljungdahlii in a continuous tank bioreactor (CSTBR), kinetics and mass transfer coefficient of carbon monoxide (CO) utilization were evaluated. Two different types of syngas and pure CO were used for CO limitation, in order to achieve high bioconversion of syngas in a single bioreactor. The CO conversion increased with an increase in gas flow rate and agitation speed. For a gas flow rate of 14 ml/min and an agitation rate of 550 rpm, the cell concentration and conversion of pure CO were 1.92 g/l and 80%, respectively. The cell concentration also increased with an increase in CO percentage in the gas phase. Maximum cell dry weight of 2 g/l and CO conversion of 93% were achieved with 70% CO blended syngas at a gas flow rate of 14 ml/min and agitation rate of 500 rpm. The total amounts of ethanol and acetate concentrations were approximately 11 g/l. The mass transfer coefficient was calculated for the culture of C. ljungdahlii with pure CO in the CSTBR. The maximum mass transfer coefficient (KLa) was 135 h-1 at an agitation speed of 550 rpm. The KLa correlation based on various gas flow rates and agitation speeds was fitted with experimental data and the predicted model was in good conformity with the obtained data.

In this study, to mimic the mineral and organic components of natural bone, hydroxyapatite[HA] and gelatin [GEL] composite scaffolds were prepared using the solvent-casting method combined with a freeze drying process. Glutaraldehyde [GA] was used as a cross linking agent and sodium bisulfite was used as an excess GA discharger. Using this technique, it is possible to produce scaffolds with mechanical and structural properties close to those of the natural trabecular bone. The prepared scaffold has an open, interconnected porous structure. It was found that the GEL/HA ratio with a 50 wt% (weight percent) HA has the compressive modulus, the ultimate compressive stress and elongation similar to those for the trabecular bone. The chemical bonding and the microstructure of the composites were investigated by FT-IR (Fourier Transform Infra Red), SEM (Scanning Electron Microscopy) and Light microscopy, indicating the presence of bonds between Ca2+ ions of HA and R-COO- ions of GEL in the HA-GEL composite scaffolds. It was found that the addition of HA content can reduce the water absorption and porosity of scaffold. The porosity and the apparent density of 50 wt% HA scaffold were also calculated. The biological responses of scaffolds were examined in L929 fibroblast cell culture, showed partially proliferation of cells around and on the composite surface.

Newcastle disease is one of the main concerns of poultry farmers. Detection of virulent strains of Newcastle disease virus (NDV) has a great impact on control measures against the disease. In this study RT-PCR was optimized in high sensitivity in order to differentiate the virulent from non-virulent NDV isolates directly in tissue homogenates. The vaccinal NDV strain and known field isolates were tested by this technique. RT-PCR was performed using two sets of primers chosen from a section of the F gene. The PCR product was cloned in to a pTZ57R/T vector and sequenced. The sequence data confirmed the specificity of the test. Detection of viral virulence was determined based on the amplification of PCR products. The above optimized RT-PCR produce can be used to confirm the diagnosis of Newcastle disease within 24 hrs using RNA isolated directly from tissue homogenate or passaged in SPF (Specific Pathogen Free) embryonated eggs.

Ataxia-Telangiectasia (AT) is a rare human neurodegenerative autosomal recessive multisystem disease that is characterized by a wide range of features including, progressive cerebellar ataxia with onset during infancy, occulocutaneous telangiectasia, susceptibility to neoplasia, occulomotor disturbances, chromosomal instability and growth and developmental abnormalities. Mitochondrial DNA (mtDNA) has the only non-coding regions at the displacement loop (D-loop) region that contains two hypervariable segments (HVS-I and HVS-II) with high polymorphism. We investigated mt-DNA deletions and haplogroups in AT patients. In this study, 24 Iranian patients suffering from AT and 100 normal controls were examined. mt-DNA was extracted from whole blood and examined by 6 primers for existence of mitochondrial deletions. We also amplified and sequenced the mtDNA HVS-I by standard sequencing techniques. mtDNA deletions were observed in 54.1% (13/24) of patients (8.9 kb deletion in all samples, 5.0 kb in one and 7.5 kb in two patients), representing mtDNA damage which may be due to oxidative stress in mitochondria. Our results showed that there is no association between mtDNA haplogroups and AT. This data may indicate involvement of mitochondrial damage in the pathogenesis of AT.