Single-Molecule Force Spectroscopy of Membrane Protein Folding

Single-molecule force spectroscopy is a unique method that can probe the structural changes of single proteins at a high spatiotemporal resolution while mechanically manipulating them over a wide force range. Here, we review the current understanding of membrane protein folding learned by using the force spectroscopy approach. Membrane protein folding in lipid bilayers is one of the most complex biological processes in which diverse lipid molecules and chaperone proteins are intricately involved. The approach of single protein forced unfolding in lipid bilayers has produced important findings and insights into membrane protein folding. This review provides an overview of the forced unfolding approach, including recent achievements and technical advances. Progress in the methods can reveal more interesting cases of membrane protein folding and clarify general mechanisms and principles.     

Comparison of different artificial neural network architectures in modeling of Chlorella sp. flocculation

Biodiesel production from microalgae feedstock should be performed after growth and harvesting of the cells, and the most feasible method for harvesting and dewatering of microalgae is flocculation. Flocculation modeling can be used for evaluation and prediction of its performance under different affective parameters. However, the modeling of flocculation in microalgae is not simple and has not performed yet, under all experimental conditions, mostly due to different behaviors of microalgae cells during the process under different flocculation conditions. In the current study, the modeling of microalgae flocculation is studied with different neural network architectures. Microalgae species, Chlorella sp., was flocculated with ferric chloride under different conditions and then the experimental data modeled using artificial neural network. Neural network architectures of multilayer perceptron (MLP) and radial basis function architectures, failed to predict the targets successfully, though, modeling was effective with ensemble architecture of MLP networks. Comparison between the performances of the ensemble and each individual network explains the ability of the ensemble architecture in microalgae flocculation modeling.     

Glutaredoxin systems

Glutaredoxins utilize the reducing power of glutathione to maintain and regulate the cellular redox state and redox-dependent signaling pathways, for instance, by catalyzing reversible protein S-glutathionylation. Due to the general importance of these processes, glutaredoxins have been implied in various physiological and disease-related conditions, such as immune defense, cardiac hypertrophy, hypoxia-reoxygenation insult, neurodegeneration and cancer development, progression as well as treatment. The past years have seen an impressive gain of knowledge regarding new glutaredoxin systems and functions. This is true both with respect to new functions in redox regulation and also with respect to unexpected new ties to iron metabolism and iron–sulfur cluster biosynthesis. The aim of this review is to provide a state-of-the-art overview over these recent discoveries with a focus on aspects related to human health.     

Development of a bionanotechnological phosphate removal system with thermostable ferritin

Phosphate removal to ecologically desired levels of <0.01 mg/L is currently dependent on large overdosing of metal salts and production of large amounts of chemical sludge. The present study focuses on the development and performance of a new bionanotechnological phosphate removal system, based on sorption of oxoanions by nanoscale ferric iron particles stabilized within thermostable ferritin from the hyperthermophilic archaeon Pyrococcus furiosus (PfFrt). Laboratory studies show that this thermostable protein nanocage has fast kinetics for phosphate uptake at very low concentrations by catalytic oxidation of iron. In this study we demonstrate essentially complete phosphate removal with a capacity of approximately 11 mg/g PfFrt. Ferritin can easily be immobilized and is amenable to fast and efficient regeneration, making recovery of phosphate possible. The phosphate removal process with PfFrt is, due to its high affinity, able to reach ecologically desired phosphate levels and in addition it is cost competitive with existing techniques. Biotechnol. Bioeng. 2010;105: 918–923. © 2009 Wiley Periodicals, Inc.     

Magnetic circular dichroism and spin equilibrium of methemoglobin and its subunits

The intensity of the Soret magnetic circular dichroism (MCD) spectra of various complexes of methemoglobin subunits (α⁺ and β⁺) as well as methemoglobin (metHb A) was correlated well with the spin states of ferric heme. Upon the subunit association, spin state transition toward higher spin was observed only in high spin derivatives and the changes in spin state were due to mainly those of β⁺ chains. The effect of an allostric effector, inositol hexaphosphate (IHP), on the MCD spectra of metHb A derivatives was observed much significantly for high spin forms than low spin ones.