Aq deformation of Gell-Mann-Okubo mass formula

We explore the possibility of deforming Gell-Mann-Okubo (GMO) mass formula within the framework of a quantized enveloping algebra. A small value of the deformation parameter is found to provide a good fit to the observed mass spectra of theπ, K andη mesons.     

On the molecular mechanism of drug intercalation into DNA: a simulation study of the intercalation pathway, free energy, and DNA structural changes

Intercalation into DNA (insertion between a pair of base pairs) is a critical step in the function of many anticancer drugs. Despite its importance, a detailed mechanistic understanding of this process at the molecular level is lacking. We have constructed, using extensive atomistic computer simulations and umbrella sampling techniques, a free energy landscape for the intercalation of the anticancer drug daunomycin into a twelve base pair B-DNA. A similar free energy landscape has been constructed for a probable intermediate DNA minor groove-bound state. These allow a molecular level understanding of aspects of the thermodynamics, DNA structural changes, and kinetic pathways of the intercalation process. Key DNA structural changes involve opening the future intercalation site base pairs toward the minor groove (positive roll), followed by an increase in the rise, accompanied by hydrogen bonding changes of the minor groove waters. The calculated intercalation free energy change is -12.3 kcal/mol, in reasonable agreement with the experimental estimate -9.4 kcal/mol. The results point to a mechanism in which the drug first binds to the minor groove and then intercalates into the DNA in an activated process, which is found to be in general agreement with experimental kinetic results.     

Use of fluorescence probes for studying Kamlet-Taft solvatochromic parameters of micellar system formed by binary mixture of sodium dodecyl sulfate and Triton-X 100

Fluorescence probes have been used to estimate Kamlet-Taft solvatochromic parameters alpha and pi* representing hydrogen-bond donation ability and dipolarity/polarizability, respectively, of sodium dodecyl sulfate (SDS)-Triton X 100 (TX100) mixed aggregates with varying compositions. The hydrogen-bond donation ability of the mixed aggregate has been found to increase with SDS composition, whereas the dipolarity/polarizability parameter decreases. The relative contribution of electrostatic and steric effect toward the total free energy of micellization have been calculated for the mixture. The solvatochromic parameters alpha and pi* depend linearly on the total free energy of micellization, indicating a correlation between aggregational and solvatochromic properties.     

Native and unfolded cytochrome c--comparison of dynamics using 2D-IR vibrational echo spectroscopy

Unfolded vs native CO-coordinated horse heart cytochrome c (h-cyt c) and a heme axial methionine mutant cyt c552 from Hydrogenobacter thermophilus ( Ht-M61A) are studied by IR absorption spectroscopy and ultrafast 2D-IR vibrational echo spectroscopy of the CO stretching mode. The unfolding is induced by guanidinium hydrochloride (GuHCl). The CO IR absorption spectra for both h-cyt c and Ht-M61A shift to the red as the GuHCl concentration is increased through the concentration region over which unfolding occurs. The spectra for the unfolded state are substantially broader than the spectra for the native proteins. A plot of the CO peak position vs GuHCl concentration produces a sigmoidal curve that overlays the concentration-dependent circular dichroism (CD) data of the CO-coordinated forms of both Ht-M61A and h-cyt c within experimental error. The coincidence of the CO peak shift curve with the CD curves demonstrates that the CO vibrational frequency is sensitive to the structural changes induced by the denaturant. 2D-IR vibrational echo experiments are performed on native Ht-M61A and on the protein in low- and high-concentration GuHCl solutions. The 2D-IR vibrational echo is sensitive to the global protein structural dynamics on time scales from subpicosecond to greater than 100 ps through the change in the shape of the 2D spectrum with time (spectral diffusion). At the high GuHCl concentration (5.1 M), at which Ht-M61A is essentially fully denatured as judged by CD, a very large reduction in dynamics is observed compared to the native protein within the approximately 100 ps time window of the experiment. The results suggest the denatured protein may be in a glassy-like state involving hydrophobic collapse around the heme.     

Photoinduced Dynamics and Toxicity of a Cancer Drug in Proximity of Inorganic Nanoparticles under Visible Light

Drug sensitization with various inorganic nanoparticles (NPs) has proved to be a promising and an emergent concept in the field of nanomedicine. Rose bengal (RB), a notable photosensitizer, triggers the formation of reactive oxygen species under green‐light irradiation, and consequently, it induces cytotoxicity and cell death. In the present study, the effect of photoinduced dynamics of RB upon complexation with semiconductor zinc oxide NPs is explored. To accomplish this, we successfully synthesized nanohybrids of RB with ZnO NPs with a particle size of 24 nm and optically characterized them. The uniform size and integrity of the particles were confirmed by high‐resolution transmission electron microscopy. UV/Vis absorption and steady‐state fluorescence studies reveal the formation of the nanohybrids. ultrafast picosecond‐resolved fluorescence studies of RB–ZnO nanohybrids demonstrate an efficient electron transfer from the photoexcited drug to the semiconductor NPs. Picosecond‐resolved Förster resonance energy transfer from ZnO NPs to RB unravel the proximity of the drug to the semiconductor at the molecular level. The photoinduced ROS formation was monitored using a dichlorofluorescin oxidation assay, which is a conventional oxidative stress indicator. It is observed that the ROS generation under green light illumination is greater at low concentrations of RB–ZnO nanohybrids compared with free RB. Substantial photodynamic activity of the nanohybrids in bacterial and fungal cell lines validated the in vitro toxicity results. Furthermore, the cytotoxic effect of the nanohybrids in HeLa cells, which was monitored by MTT assay, is also noteworthy.     

Hydrazine selective dual signaling chemodosimetric probe in physiological conditions and its application in live cells

A rhodamine–cyanobenzene conjugate, (E)-4-((2-(3′,6′-bis(diethylamino)-3-oxospiro[isoindoline-1,9′-xanthene]-2-yl)ethylimino)methyl)benzonitrile (1), which structure has been elucidated by single crystal X-ray diffraction, was synthesized for selective fluorescent “turn-on” and colorimetric recognition of hydrazine at physiological pH 7.4. It was established that 1 detects hydrazine up to 58 nM. The probe is useful for the detection of intracellular hydrazine in the human breast cancer cells MCF-7 using a fluorescence microscope. Spirolactam ring opening of 1, followed by its hydrolysis, was established as a probable mechanism for the selective sensing of hydrazine.