Identification of Folding Intermediates of Streblin,The Most Stable Serine Protease: Biophysical Analysis

Streblin, a serine proteinase from plant Streblus asper, has been used to investigate the conformational changes induced by pH, temperature, and chaotropes. The near/far UV circular dichroism activities under fluorescence emission spectroscopy and 8-aniline-1-naphthalene sulfonate (ANS) binding have been carried out to understand the unfolding of the protein in the presence of denaturants. Spectroscopic studies reveal that streblin belongs to the α+β class of proteins and exhibits stability towards chemical denaturants, guanidine hydrochloride (GuHCl). The pH-induced transition of this protein is noncooperative for transition phases between pH 0.5 and 2.5 (midpoint, 1.5) and pH 2.5 and 10.0 (midpoint, 6.5). At pH 1.0 or lower, the protein unfolds to form acid-unfolded state, and for pH 7.5 and above, protein turns into an alkaline denatured state characterized by the absence of ANS binding. At pH 2.0 (1 M GuHCl), streblin exists in a partially unfolded state with characteristics of a molten globule state. The protein is found to exhibit strong and predominant ANS binding. In total, six different intermediate states has been identified to show protein folding pathways.     

Origin of charge density wave formation in insulators from a high resolution photoemission study of BaIrO3

We investigate the origin of charge density wave (CDW) formation in insulators by studying BaIrO3 using high-resolution (1.4 meV) photoemission spectroscopy. The spectra reveal the existence of localized density of states at the Fermi level, E(F), in the vicinity of room temperature. These localized states are found to vanish as the temperature is lowered, thereby, opening a soft gap at E(F), as a consequence of CDW transition. In addition, the energy dependence of the spectral density of states reveals the importance of magnetic interactions, rather than well-known Coulomb repulsion effect, in determining the electronic structure thereby implying a close relationship between ferromagnetism and CDW observed in this compound. Also, Ba core level spectra surprisingly exhibit an unusual behavior prior to CDW transition.     

KLL Auger resonant Raman transition in metallic Cu and Ni

High energy resolution KL₂₃L₂₃ Auger spectra of polycrystalline Cu and Ni were measured using photon energies up to about 50 eV above the K-absorption edge and down to 5 eV (Cu KLL) and 4 eV (Ni KLL) below threshold. The spectra show strong satellite structures varying considerably as a function of the photon energy. In the sub-threshold region the linear dispersion of the diagram line energy positions and a distortion of the line shape as a function of photon energy, attributable to the Auger resonant Raman process, is clearly observed, indicating the one-step nature of the Auger emission. These changes in the resonant spectra are interpreted using a simple model based on resonant scattering theory in combination with partial density of states obtained from cluster molecular orbital (DV-Xα) calculations.     

Some polishing experiments on copper in a hyperbolic cell

Some polishing experiments have been carried out on copper anodes in a hyperbolic cell designed by Gilmont and Walton, using orthophosphoric acid as the electrolyte. The results obtained have been compared to those obtained in similar experiments in a Hull cell. It has been found that very similar bands of different reflectivity and polishes are found to form in both the cells. These bands shift with time and a study of such displacements has been made. The results are briefly discussed.     

Revelation of the role of impurities and conduction electron density in the high resolution photoemission study of ferromagnetic hexaborides

We investigate the temperature evolution of the electronic structure of ferromagnetic CaB6 using ultrahigh resolution photoemission spectroscopy; the electronic structure of paramagnetic LaB6 is used as a reference. High resolution spectra of CaB6 reveal a finite density of states at the Fermi level E(F) at all the temperatures and evidence of impurity induced localized features in the vicinity of E(F), which are absent in the spectra of LaB6. Analysis of the high resolution spectra suggests that disorder in the B sublattice inducing partial localization in the mobile electrons and low electron density at E(F) is important to achieve ferromagnetism in these systems.     

Size effect study in magnetoelectric BiFeO3 system

In this paper, we report for the first time finite size effects on Néel temperature (T _N) of magnetoelectric BiFeO₃ system. Novel wet chemical route has been developed to produce fine particles of BiFeO₃ with controlled size and size distribution. Unlike other oxide systems, lattice volume contraction has been observed with decrease in particle size. The decrease in T _N is co-related to unit cell volume contraction occurring with reduction in particle size.     

Chromatographic Techniques for the Separation of Peptides: Application to Proteomics

The greatest challenge for proteomics is the inherently complex nature of cellular proteomes as they are highly dynamic entities. High performance liquid chromatography is an indispensable tool in proteomics research, providing high-speed, high sensitivity separation and good resolution of proteins and peptides. Chromatographic sciences have played an animated, bustling and critical role in many fields, the next challenging analytical project for the chromatographic scientists is in the area of proteomics. Which type of analysis best determines the optimal separation technique for any proteomic study? The aim of this review is to outline the different chromatographic strategies that have been employed for analysis of complex mixtures of proteins/peptides, highlighting the role of liquid chromatography coupled to mass spectrometry.     

Insights into pH-Induced Conformational Transition of <Emphasis Type="Italic">β</Emphasis>-Galactosidase from <Emphasis Type="Italic">Pisum sativum</Emphasis> Leading to its Multimerization

Although β-galactosidases are physiologically a very important enzyme and have may therapeutics applications, very little is known about the stability and the folding aspects of the enzyme. We have used β-galactosidase from Pisum sativum (PsBGAL) as model system to investigate stability, folding, and function relationship of β-galactosidases. PsBGAL is a vacuolar protein which has a tendency to multimerize at acidic pH with protein concentration ≥100 μg mL⁻¹ and dissociates into its subunits above neutral pH. It exhibits maximum activity as well as stability under acidic conditions. Further, it has different conformational orientations and core secondary structures at different pH. Substantial predominance of β-content and interfacial interactions through Trp residues play crucial role in pH-dependent multimerization of enzyme. Equilibrium unfolding of PsBGAL at acidic pH follows four-state model when monitored by changes in the secondary structure with two intermediates: one resembling to molten globule-like state while unfolding seen from activity and tertiary structure of PsBGAL fits to two-state model. Unfolding of PsBGAL at higher pH always follows two-state model. Furthermore, unfolding of PsBGAL reveals that it has at least two domains: α/β barrel containing catalytic site and the other is rich in β-content responsible for enzyme multimerization.     

Optimization of Fermentation Parameters to Enhance the Production of Ethanol from Palmyra Jaggery Using <Emphasis Type="Italic">Saccharomyces cerevisiae</Emphasis> in a Batch Fermentor

Application of statistical experimental designs for optimization of fermentation parameters to enhance ethanol production, which is an economical and renewable energy source using Saccharomyces cerevisiae NCIM 3090 from palmyra jaggery, was studied in a batch fermentor. Using Plackett–Burman design, impeller speed, concentrations of CoCl₂ and KH₂PO₄ were identified as significant variables, which highly influenced ethanol production, and these variables were further optimized using a central composite design (CCD). The ethanol production was adequately approximated with a full quadratic equation obtained from three factors and five levels of CCD. Maximum ethanol concentration of 132.56 g/l (16.8% [v/v]) was obtained for an impeller speed of 247.179 (≈250) rev/min, CoCl₂ of 0.263 g/l and KH₂PO₄ of 2.39 g/l. A second-order polynomial regression model was fitted and was found adequate with R ² of 0.8952. This combined statistical approach enables rapid identification and investigation of significant parameters for improving the ethanol production and could be very useful in optimizing processes.