Thermal and Structural Stability of Adsorbed Proteins

Experimental evidence suggests that proteins adsorbed to hydrophobic surfaces at low coverages are stabilized relative to the bulk. For larger coverages, proteins unfold and form β-sheets. We performed computer simulations on model proteins and found that: 1), For weakly adsorbing surfaces, unfolded conformations lose more entropy upon adsorption than folded ones. 2), The melting temperature, both in the bulk and at surfaces, decreases with increasing protein concentration because of favorable interprotein interactions. 3), Proteins in the bulk show large unfolding free energy barriers; this barrier decreases at stronger adsorbing surfaces. We conjecture that typical experimental temperatures appear to be below the bulk melting temperature for a single protein, but above the melting temperature for concentrated protein solutions. Purely thermodynamic factors then explain protein stabilization on adsorption at low concentrations. However, both thermodynamic and kinetic factors are important at higher concentrations. Thus, proteins in the bulk do not denature with increasing concentration due to large kinetic barriers, even though the aggregated state is thermodynamically preferred. However, they readily unfold upon adsorption, with the surface acting as a heterogeneous catalyst. The thermal behavior of proteins adsorbed to hydrophobic surfaces thus appears to follow behavior independent of their chemical specificity.     

A comparison of liquid-holding recovery and photoreactivation in halophilic and non-halophilic bacteria

The ability of the extreme halophile Halobacterium cutirubrum to recover from the effects of ultraviolet radiation during liquid holding in the dark in non-nutrient medium has been compared with that of (i) a moderately halophilic bacterium (NRC 41227) and (ii) Escherichia coli B. The photoreactivabilities of all three bacteria have also been studied. The extreme halophile was incapable of liquid-holding recovery in these conditions, in marked contrast to both E. coli B and the moderate halophile, and also failed to recover when held in nutrient medium in the dark. These results strongly support the hypothesis that H. cutirubrum lacks DNA excision repair. It was also found that ultraviolet-irradiated H. cutirubrum could be almost completely photoreactivated from any level of survival in the range 10(-4)-80%, provided exposure to visible light was not delayed, whereas the moderate halophile resembled E. coli B and had a comparatively limited capacity for photoreactivation.     

The effect of age on enolase turnover in the free-living nematode, Turbatrix aceti.

The rates of synthesis and degradation of enolase and total soluble proteins slow with age in the free-living nematode, Turbatrix aceti. The half-lives are 73 and 58 h for soluble protein and enolase, respectively, in young organisms (5 days old). The respective figures are 163 and 161 h for old organisms (22–30 days old). Similar slowing of protein turnover occurs when the organisms are aged by a repeated screening procedure which avoids the use of fluorodeoxyuridine, an inhibitor of DNA synthesis normally added to aging cultures to obtain synchrony. The results support the idea that slowed protein turnover may be responsible for the formation of altered enzymes in old organisms.     

Biochemical analysis and synergistic suppression of indoxacarb resistance in Plutella xylostella L.

Indoxacarb was treated to Plutella xylostella for 10 generations to develop a resistant strain and biochemical analysis of indoxacarb resistance in different tissues of P. xylostella was carried out. Biochemical analysis found maximum esterase activity in gut homogenates of indoxacarb resistant strains followed by whole body and cuticle homogenates. In gut homogenates of indoxacarb resistant strains, maximum increase in esterases was found as compared to the unselected strain. Acetylcholineesterase activity was higher in head homogenates of the resistant strain than in the unselected strain. Glutathione-S-transferase activity was highest in whole body homogenates. However, maximum increase was found in gut homogenates of indoxacarb resistant strains over the unselected. Induced resistance was suppressed using known synergists. Maximum synergism occurred using diethyl-maleate (DEM), followed by triphenyl phosphate (TPP).     

Tissue distribution of high molecular weight calmodulin-binding protein

Polyclonal antibodies raised against bovine heart high molecular weight calmodulin-binding protein were used to study the distribution of this protein in diverse bovine tissues. The high molecular weight calmodulin-binding protein, in addition to bovine heart, is also present in lung and brain at much lower levels, but not in skeletal muscle, spleen, kidney or uterus.     

Assessment of bacterial diversity in agricultural by-product compost by sequencing of cultivated isolates and amplified rDNA restriction analysis

An investigation of bacterial diversity in compost was performed using molecular chronometer in order to reveal its phylogeny. Thirty-three bacterial isolates isolated from compost were analyzed by 16S rRNA gene sequencing which revealed phylogenetic lineage of class Bacilli, γ, β-Proteobacteria, and Actinobacteria. Among these lineages, isolates belonging to class Bacilli consisted of species from genera Staphylococcus, Bacillus, Terribacillus, and Lysinibacillus. From phylum Actinobacteria: Microbacterium barkeri and Kocuria sp. were identified. Other bacterial groups had phylogenetic linkage with genera Comamonas and Acidovorax (class β-Proteobacteria); Serratia, Klebsiella, and Enterobacter (class γ-Proteobacteria). Similar isolates were analyzed through ARDRA. Amplified product of 16S rRNA gene from each isolates was subjected to cleavage by enzymes HpaII, HinfI, and MspI in separate reaction tubes. HpaII generated 2–6 bands ranging from 90–688 bp, HinfI generated 2–5 bands of 71–1,038 bp, and MspI 2–7 bands of 69–793 bp. The restriction patterns from HpaII, HinfI, and MspI were normalized separately and combined by means of pattern recognition software “Diversity Database.” HpaII had highest discrimination index (0.72) than HinfI (0.68) and MspI (0.65), and the combination of all three showed discrimination index (0.69). Numerical analysis of ARDRA patterns demonstrated sufficient phylogenetic information for characterizing bacterial diversity. Phylogenetic relationship obtained among isolates through ARDRA was compared with 16S rRNA gene sequence and ARDRA results showed sufficiently similar 16S rRNA gene sequence analysis, but not an overlapping. It has been observed that ARDRA technique facilitates the identification of bacteria in less than 36 h as compared to traditional 16S rRNA gene sequencing.     

Wastewater: A Potential Bioenergy Resource

Wastewaters are a rich source of nutrients for microorganisms. However, if left unattended the biodegradation may lead to severe environmental hazards. The wastewaters can thus be utilized for the production of various value added products including bioenergy (H₂ and CH₄). A number of studies have reported utilization of various wastewaters for energy production. Depending on the nature of the wastewater, different reactor configurations, wastewater and inoculum pretreatments, co-substrate utilizations along with other process parameters have been studied for efficient product formation. Only a few studies have reported sequential utilization of wastewaters for H₂ and CH₄ production despite its huge potential for complete waste degradation.     

Heterogeneity in buffalo lutropin.

Lutropin (LH-1) from water buffaloes has been shown to exhibit microheterogeneity in the N-terminal amino-acid sequence of its alpha-subunit. The beta-subunit did not exhibit such microheterogeneity. Another protocol of purification yielded a preparation of buffalo LH (bu LH-2) different from the buffalo LH-1 in certain physico-chemical properties like ease of dissociation into subunits, sugar composition, isoelectric point, and elution profile on S-200. Data appear to indicate the presence of more than one form of buffalo lutropin.