An angular motion of a conserved four-helix bundle facilitates alternating access transport in the TtNapA and EcNhaA transporters.

There is ongoing debate regarding the mechanism through which cation/proton antiporters (CPAs), like NapA (TtNapA) and Escherichia coli NapA (EcNhaA), alternate between their outward- and inward-facing conformations in the membrane. CPAs comprise two domains, and it is unclear whether the transition is driven by their rocking-bundle or elevator motion with respect to each other. Here we address this question using metadynamics simulations of TtNapA, where we bias conformational sampling along two axes characterizing the two proposed mechanisms: angular and translational motions, respectively.

Cardiolipin is an Optimal Phospholipid for the Assembly, Stability, and Proper Functionality of the Dimeric Form of NhaA Na/H Antiporter.

Cardiolipin (CL) was shown to bound to the dimer interface of NhaA Na/H antiporter. Here, we explore the cardiolipin-NhaA interaction both in vitro and in vivo. Using a novel and straightforward in-vitro assay in which n-dodecyl β-D maltoside (DDM) detergent is used to delipidate the dimer interface and to split the dimers into monomers; the monomers are subsequently exposed to cardiolipin or the other E.

Triblock-Copolymer-Assisted Mixed-Micelle Formation Results in the Refolding of Unfolded Protein.

The present work reports a new strategy for triblock-copolymer-assisted refolding of sodium dodecyl sulfate (SDS)-induced unfolded serum protein human serum albumin (HSA) by mixed-micelle formation of SDS with poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) triblock copolymer EOPOEO (P123) under physiological conditions. The steady-state and time-resolve fluorescence results show that the unfolding of HSA induced by SDS occurs in a stepwise manner through three different phases of binding of SDS, which is followed by a saturation of interaction. Interestingly, the addition of polymeric surfactant P123 to the unfolded protein results in the recovery of ∼87% of its α-helical structure, which was lost during SDS-induced unfolding.

Contrasting effects of pH on the modulation of the structural integrity of hemoglobin induced by sodium deoxycholate.

Bile salt-mediated conformational modification of hemoglobin (Hb) was examined at three different pHs i.e., 3.

Contrasting Effects of Salt and Temperature on Niosome-Bound Norharmane: Direct Evidence for Positive Heat Capacity Change in the Niosome:β-Cyclodextrin Interaction.

The modulation of the prototropic equilibrium of a cancer cell photosensitizer, norharmane (NHM), within a niosome microheterogeneous environment has been investigated. The contrasting effects of temperature and extrinsically added salt on the photophysics of niosome-bound drug have been meticulously explored from steady-state and time-resolved spectroscopic techniques. The cation ⇌ neutral prototropic equilibrium of NHM is found to be preferentially favored toward the neutral species with increasing salt concentration, and the results are rationalized on the basis of water penetration to the hydration layer of niosome.

Inverse Temperature Dependence in Static Quenching versus Calorimetric Exploration: Binding Interaction of Chloramphenicol to β-Lactoglobulin.

The binding interaction between the whey protein bovine β-lactoglobulin (βLG) with the well-known antibiotic chloramphenicol (Clp) is explored by monitoring the intrinsic fluorescence of βLG. Steady-state and time-resolved fluorescence spectral data reveal that quenching of βLG fluorescence proceeds through ground state complex formation, i.e.

A critical approach toward resonance-assistance in the intramolecular hydrogen bond interaction of 3,5-diiodosalicylic acid: a spectroscopic and computational investigation.

The photophysics of a prospective drug molecule, 3,5-diiodosalicylic acid (3,5-DISA), having a wide spectrum of biological and medicinal applications, have been investigated using spectroscopic techniques and computational analyses. The remarkably large Stokes' shifts in various solvents from 3,5-DISA has been intertwined with the occurrence of an excited-state intramolecular proton transfer (ESIPT) reaction. Concurrently, the emergence of an intriguing dual emission feature in less interacting solvents is also reported and the spectral response of 3,5-DISA toward the variation of medium acidity/basicity has been exploited to decipher the nature of various species present in different solvents.

Hydrophobicity is the governing factor in the interaction of human serum albumin with bile salts.

The present study demonstrates a detailed characterization of the interaction of a series of bile salts, sodium deoxycholate (NaDC), sodium cholate (NaC), and sodium taurocholate (NaTC), with a model transport protein, human serum albumin (HSA). Here, steady-state and time-resolved fluorescence spectroscopic techniques have been used to characterize the interaction of the bile salts with HSA. The binding isotherms constructed from steady-state fluorescence intensity measurements demonstrate that the interaction of the bile salts with HSA can be characterized by three distinct regions, which were also successfully reproduced from the significant variation of the emission wavelength (λ(em)) of the intrinsic tryptophan (Trp) moiety of HSA.

Temperature induced morphological transitions from native to unfolded aggregated States of human serum albumin.

The circulatory protein, human serum albumin (HSA), is known to have two melting point temperatures, 56 and 62 °C. In this present manuscript, we investigate the interaction of HSA with a synthesized bioactive molecule 3-pyrazolyl 2-pyrazoline (PZ). The sole tryptophan amino acid residue (Trp214) of HSA and PZ forms an excellent FRET pair and has been used to monitor the conformational dynamics in HSA as a function of temperature.