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The binding interaction of milk protein β-lactoglobulin (β-LG) with plant alkaloid berberine (BER) has been thoroughly investigated using spectroscopic, calorimetric, and small-angle X-ray scattering studies aided by computational methods. The electronic UV-Vis and steady-state fluorescence spectroscopy experiments have suggested the creation of a ground-state complex between β-LG and BER. The origin of protein fluorescence is identified to be from Trp19, which is located in the hydrophobic pocket of β-LG. Time-resolved fluorescence spectroscopy confirmed the static quenching of β-LG fluorescence in the presence of BER. Binding parameters allied with the β-LG – BER complex have been estimated from the spectroscopic studies and correlated with the results directly obtained from isothermal titration calorimetry (ITC) studies. The fluorescence resonance energy transfer (FRET) from β-LG to BER has been explored. The synchronous fluorescence measurement has revealed variations in the microenvironment of the tyrosine and tryptophan residues of β-LG in the presence of BER. Circular dichroism (CD) results have revealed no or minimal conformational changes in the secondary structure of β-LG dimer due to the interaction with the BER molecule. The detailed small-angle X-ray scattering (SAXS) data further presages minimal structural alterations of β-LG in the presence of BER. Theoretical docking and molecular dynamics simulation investigations validated the experimental findings. The detailed investigation of β-LG – BER binding interactions may allow β-LG – BER or other protein–alkaloid complexes as potential drug carriers against various diseases as the protein structure is almost retained in the interaction. [ABSTRACT FROM AUTHOR]

Type Three Secretion System (T3SS) is a sophisticated nano‐scale weapon utilized by several gram negative bacteria under stringent spatio‐temporal regulation to manipulate and evade host immune systems in order to cause infection. To the best of our knowledge, this present study is the first report where we embark upon characterizing inherent features of native type three secretion effector protein PemB through biophysical techniques. Herein, first, we demonstrate binding affinity of PemB for phosphoinositides through isothermal calorimetric titrations. Second, we shed light on its strong homo‐oligomerization propensity in aqueous solution through multiple biophysical methods. Third, we also employ several spectroscopic techniques to delineate its disordered and helical conformation. Lastly, we perform a phylogenetic analysis of this new effector to elucidate evolutionary relationship with other organisms. Taken together, our results shall surely contribute to our existing knowledge of Pseudomonas aeruginosa secretome. [ABSTRACT FROM AUTHOR]

Quantum chemical calculations have been carried out to explore structural and spectroscopic properties of some derivatives of N-iso-butyl, S-2-nitro-1-phenylethyl dithiocarbamate molecule in neutral and cationic forms. Electron-releasing groups (Me, OH and OMe) are considered to explore their effect on geometrical parameters, vibrational spectra and electronic properties of N-iso-butyl, S-2-nitro-1-phenylethyl dithiocarbamate. All the computations were performed at DFT/B3LYP level of Gaussian09 suite. The Raman spectra at different laser exciting frequencies are presented. The potential energy distributions of the considered derivatives were calculated by using the normal coordinate analysis method. The NBO calculations were performed to study the donor-acceptor interactions, HOMO-LUMO, electronic structure and hyper-conjugative interaction energies. The vibrational contribution of various thermodynamical parameters, viz, entropy, specific heat and free energy have also been presented and discussed in detail. Moreover, we have also explored the effect of temperature at specific heat and partition function of these molecules. Molecular docking studies have been performed to understand the nature of the interactions and the probable binding sites of NSD, NSD-Me, NSD-OH and NSD-OMe molecules in the active pockets of the 2KCE receptor. [ABSTRACT FROM AUTHOR]

Type Three Secretion System (T3SS) is a sophisticated nano-scale weapon utilized by several gram negative bacteria under stringent spatio-temporal regulation to manipulate and evade host immune systems in order to cause infection. To the best of our knowledge, this present study is the first report where we embark upon characterizing inherent features of native type three secretion effector protein PemB through biophysical techniques. Herein, first, we demonstrate binding affinity of PemB for phosphoinositides through isothermal calorimetric titrations. Second, we shed light on its strong homo-oligomerization propensity in aqueous solution through multiple biophysical methods. Third, we also employ several spectroscopic techniques to delineate its disordered and helical conformation. Lastly, we perform a phylogenetic analysis of this new effector to elucidate evolutionary relationship with other organisms. Taken together, our results shall surely contribute to our existing knowledge of Pseudomonas aeruginosa secretome., (© 2023 The Protein Society.)