A novel DNA hairpin substrate for bleomycin

A 16-nucleotide DNA hairpin containing 4-aminobenzo[g]quinazoline-2-one 2'-deoxyribose at position 15 has been prepared and found to lack significant fluorescence. When treated with Fe(II).BLM, the hairpin was found to undergo oxidative transformation selectively at position 15. The predominant fluorescent product was characterized and quantified. The pro-fluorescent DNA hairpin was used as a substrate for 15 bleomycin congeners, and the results were compared with those obtained following cleavage of a radiolabeled DNA duplex and PAGE analysis.     

Inorganic analysis of biological fluids using capillary electrophoresis

This review article focuses on recent advances of CE in determination of inorganic species in biological fluids and covers the years of dedicated research in the field since 2001 when a previous similar review was published. The most productive area, in which CE has distinctively progressed over the review period, encompasses assaying major inorganic anions and cations in blood serum and urine. Other applications include assessing less abundant analytes, e. g., heavy metals or seleno-compounds, and less abundant body fluids (saliva, sweat, etc.). Special emphasis is placed on developments in CE methodology that comprised modifications of separation and detection hardware and using specific electrolyte modifiers to enhance the resolution of a CE system. Significant progress in the application of in-line preconcentration methods in order to move CE ahead closer to trace analyte levels is also brought into focus. A series of tables detailing highly developed CE procedures and the analytical figures of merit accomplished are included. Finally discussed are further strategies for the method's expansion in the practice of biomedical and clinical laboratories where CE could likely acquire the status of a benchmark analytical technique.     

Small ball probabilities for Gaussian random fields and tensor products of compact operators

We find the logarithmic -small ball asymptotics for a large class of zero mean Gaussian fields with covariances having the structure of ``tensor product'. The main condition imposed on marginal covariances is the regular behavior of their eigenvalues at infinity that is valid for a multitude of Gaussian random functions including the fractional Brownian sheet, Ornstein - Uhlenbeck sheet, etc. So we get the far-reaching generalizations of well-known results by Csáki (1982) and by Li (1992). Another class of Gaussian fields considered is the class of additive fields studied under the supremum-norm by Chen and Li (2003). Our theorems are based on new results on spectral asymptotics for the tensor products of compact self-adjoint operators in Hilbert space which are of independent interest.

     

Single-molecule observations of surfactant diffusion at the solution-solid interface

Individual fatty acid molecules adsorbed at the interface between hexadecane and fused silica have been tracked using total internal reflection fluorescence microscopy. Two cooperative diffusive mechanisms are observed: continuous small-scale Brownian motion and occasional large "jumps." The continuous diffusion exhibits evidence of confinement. The effective interfacial diffusion coefficients for each mechanism increase systematically with temperature; an Arrhenius analysis gives an activation barrier of approximately 50 kJ/mol for "jumping" and an upper limit of approximately 10 kJ/mol for confined diffusion.     

Surface protonation at the rutile (110) interface: explicit incorporation of solvation structure within the refined MUSIC model framework

The detailed solvation structure at the (110) surface of rutile (alpha-TiO2) in contact with bulk liquid water has been obtained primarily from experimentally verified classical molecular dynamics (CMD) simulations of the ab initio-optimized surface in contact with SPC/E water. The results are used to explicitly quantify H-bonding interactions, which are then used within the refined MUSIC model framework to predict surface oxygen protonation constants. Quantum mechanical molecular dynamics (QMD) simulations in the presence of freely dissociable water molecules produced H-bond distributions around deprotonated surface oxygens very similar to those obtained by CMD with nondissociable SPC/E water, thereby confirming that the less computationally intensive CMD simulations provide accurate H-bond information. Utilizing this H-bond information within the refined MUSIC model, along with manually adjusted Ti-O surface bond lengths that are nonetheless within 0.05 A of those obtained from static density functional theory (DFT) calculations and measured in X-ray reflectivity experiments (as well as bulk crystal values), give surface protonation constants that result in a calculated zero net proton charge pH value (pHznpc) at 25 degrees C that agrees quantitatively with the experimentally determined value (5.4+/-0.2) for a specific rutile powder dominated by the (110) crystal face. Moreover, the predicted pHznpc values agree to within 0.1 pH unit with those measured at all temperatures between 10 and 250 degrees C. A slightly smaller manual adjustment of the DFT-derived Ti-O surface bond lengths was sufficient to bring the predicted pHznpcvalue of the rutile (110) surface at 25 degrees C into quantitative agreement with the experimental value (4.8+/-0.3) obtained from a polished and annealed rutile (110) single crystal surface in contact with dilute sodium nitrate solutions using second harmonic generation (SHG) intensity measurements as a function of ionic strength. Additionally, the H-bond interactions between protolyzable surface oxygen groups and water were found to be stronger than those between bulk water molecules at all temperatures investigated in our CMD simulations (25, 150 and 250 degrees C). Comparison with the protonation scheme previously determined for the (110) surface of isostructural cassiterite (alpha-SnO2) reveals that the greater extent of H-bonding on the latter surface, and in particular between water and the terminal hydroxyl group (Sn-OH) results in the predicted protonation constant for that group being lower than for the bridged oxygen (Sn-O-Sn), while the reverse is true for the rutile (110) surface. These results demonstrate the importance of H-bond structure in dictating surface protonation behavior, and that explicit use of this solvation structure within the refined MUSIC model framework results in predicted surface protonation constants that are also consistent with a variety of other experimental and computational data.