Herein we report the effect of different nucleobase pair compositions on the association-induced fluorescence enhancement property of Thioflavin T (ThT), upon binding with 20 base pair long double-stranded DNA (dsDNA). Analysis of binding and decay constants along with the association (K ass ) and dissociation (K diss ) rate constants obtained from the fluctuation in the fluorescence intensity of ThT after binding with different DNA revealed selective affinity of ThT toward AT-rich dsDNA. Molecular docking also substantiates the experimental results. We also observed that addition of orange-emitting ethidium bromide (EtBr) to cyan-emitting ThT−DNA complexes leads to bright white light emission (WLE) through Forster resonance energy transfer. Additionally, the emission of white light is far greater in the case of intra-DNA strands. Besides endorsing the binding insights of ThT to AT-rich dsDNA, the present investigations open a new perspective for realizing promising WLE from two biomarkers without labeling the DNA.
At the ALADIN-LAND setup at GSI the unbound nucleus 13 Be has been produced in one-neutron knockout reactions from a 304 MeV/nucleon relativistic beam of 14 Be ions impinging on a liquid hydrogen target. An analysis of the data including all available information about 13 Be, and in particular recent data from a similar experiment performed at RIKEN, has been performed. A consistent description is reached. It is found that the excitation spectrum is dominated by s-waves at low energy, which solves problems from previous seemingly contradictory interpretations. A possible interference between two s-states in 13 Be is also discussed. The results indicate that the ground-state wave function of 14 Be is dominated by valence neutrons in the s-shell contributing with 60-75% of the total neutron knockout cross section.
Coulomb breakup at high energy in inverse kinematics of proton-rich 31 Cl was used to constrain the thermonuclear 30 S(p,γ ) 31 Cl capture reaction rate under typical Type I x-ray burst conditions. This reaction is a bottleneck during rapid proton-capture nucleosynthesis (rp process), where its rate depends predominantly on the nuclear structure of 31 Cl. Two low-lying states just above the proton-separation threshold of S p = 296(50) keV in 31 Cl have been identified experimentally using the R 3 B-LAND setup at the GSI Helmholtzzentrum für Schwerionenforschung GmbH. Both states are considered to play a key role in the thermonuclear 30 S(p,γ ) 31 Cl capture reaction. Excitation energies of the first J π = 1/2 + ,5/2 + states have been extracted and the reaction rate for proton capture on 30 S under typical rp-process temperatures has been investigated.
Herein we report the binding interactions
between lysozyme (Lyz)
and an anthracycline drug, epirubicin hydrochloride (EPR), through
an extensive spectroscopic approach at both ensemble average and single
molecular resolution. Our steady-state and time-resolved fluorescence
spectroscopy reveals that the drug-induced fluorescence quenching
of the protein proceeds through a static quenching mechanism. Isothermal
titration calorimetry (ITC) and steady-state experiments reveal almost
similar thermodynamic signatures of the drug–protein interactions.
The underlying force that plays pivotal roles in the said interaction
is hydrophobic in nature, which is enhanced in the presence of a strong
electrolyte (NaCl). Circular dichroism (CD) spectra indicate that
there is a marginal increase in the secondary structure of the native
protein (α-helical content increases from 26.9 to 31.4% in the
presence of 100 μM EPR) upon binding with the drug. Fluorescence
correlation spectroscopy (FCS) was used to monitor the changes in
structure and conformational dynamics of Lyz upon interaction with
EPR. The individual association (K
ass =
0.33 × 106 ms–1 M–1) and dissociation (K
diss = 1.79 ms–1) rate constants and the binding constant (K
b = 1.84 × 105 M–1) values, obtained from fluctuations of fluorescence intensity of
the EPR-bound protein, have also been estimated. AutoDock results
demonstrate that the drug molecule is encapsulated within the hydrophobic
pocket of the protein (in close proximity to both Trp62 and Trp108)
and resides ∼20 Å apart from the covalently labelled CPM
dye. Förster resonance energy transfer (FRET) studies proved
that the distance between the donor (CPM) and the acceptor (EPR) is
∼22 Å, which is very similar to that obtained from molecular
docking analysis (∼20 Å). The system also shows temperature-dependent
reversible FRET, which may be used as a thermal sensor for the temperature-sensitive
biological systems.
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