DNA microarrays: tools for the 21st Century

Profiling of gene expression patterns with microarray technology is widely used in both basic and applied research. DNA microarrays have also shown great promise in clinical medicine and are paving the way toward effective pharmaceutical drug discovery and individualized drug regimens. With growing utilization of this high-throughput technology, new applications are making headlines on a regular basis. This review aims to outline the pros and cons of this methodology and direct the reader towards available useful resources. Various major array formats such as high-density oligonucleotide arrays and spotted cDNA arrays are examined, and advantages and options for using each format are presented. Factors important for the design and analysis of microarray experiments are also discussed.     

Influence of disorder on superconductivity in non-magnetic rare-earth nickel borocarbides

The effect of substitutional disorder on the superconducting properties of YNi₂B₂C was studied by partially replacing yttrium and nickel by Lu and Pt, respectively. For the two series of (Y, Lu)Ni₂B₂C and Y(Ni, Pt)₂B₂C compounds, the upper critical field H _c2(T) and the specific heat c _p(T, H) in the superconducting mixed state have been investigated. Disorder is found to reduce several relevant quantities such as T _c, the upper critical field H _c2(0) at T=0 and a characteristic positive curvature of H _c2(T) observed for these compounds near T _c. The H _c2(T) data point to the clean limit for (Y, Lu) substitutions and to a transition to the quasi-dirty limit for (Ni, Pt) substitutions. The electronic specific heat contribution γ(H) exhibits significant deviations from the usual linear γ(H) law. These deviations reduce with growing substitutional disorder but remain even in the quasidirty limit which is reached in the Y(Ni_1−x , Pt _x )₂B₂C samples for x=0.1.     

Surface modification of poly(tetrafluoroethylene) with benzophenone and sodium hydride by ultraviolet irradiation

Poly(tetrafluoroethylene) (PTFE) films were surface modified in a solution of benzophenone and sodium hydride in dry dimethylformamide by ultraviolet (UV) light irradiation. The extent of surface modification was characterized after durations of UV light irradiation from 5–20 min at temperatures from 19–60°C. The modified films were analyzed by electron spectroscopy for chemical analysis, diffuse reflectance ultraviolet-visible light spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, dynamic contact angle measurement, and low-voltage scanning electron microscopy. PTFE surfaces produced by this modification demonstrated extensive defluorination, oxygen incorporation, surface unsaturation, and reduction in both advancing and receding dynamic water contact angles in a manner that was more extensive at long durations of irradiation and at high temperatures. Morphological damage depended upon treatment conditions, but extensive surface modification could be obtained without substantial morphological damage to PTFE films. Control experiments indicated that the surface modification proceeded by photoexcitation of either diphenyl ketyl radical anion or benzhydrol anion, the products of reaction of benzophenone with sodium hydride. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1499–1514, 1997     

Non-resonant microwave absorption studies of superconducting MgB2 and MgB2 + MgO

Non-resonant microwave absorption (NRMA) studies of superconducting MgB₂ and a sample containing ∼10% by weight of MgO in MgB₂ are reported. The NRMA results indicate near absence of intergranular weak links in the pure MgB₂ sample. A linear temperature dependence of the lower critical field H _c1 is observed indicating a non-s wave superconductivity. However, the phase reversal of the NRMA signal which could suggest d wave symmetry is also not observed. In the MgB₂ + MgO sample, much larger low field dependent absorption is observed indicating the presence of intergranular weak links. The hysteretic behavior of NRMA is compared and contrasted in the two samples. In the pure MgB₂ sample, a large hysteresis is observed between the forward and the reverse scans of the magnetic field indicating strong pinning of flux lines. This hysteresis saturates a few degrees below T _c while in the MgB₂ + MgO sample, a much slower increase of hysteresis with decreasing temperature is observed, a signature of weaker pinning.     

Conformational changes of protein adsorbed on polyurethane studied by ftir-atr spectroscopy

We have studied the adsorption of human serum albumin and human gamma globulins onto a polyurethane (Pellethane 2363-80A) using an attenuated total reflectance (ATR) flow cell. Spectra of the proteins adsorbed onto the polyurethane surface, and of the same proteins in solution were collected for comparison. Significant spectral differences between the solution and surface adsorbed spectra of both proteins were observed.     

Infrared spectroscopy analysis of the structure of multilayer Langmuir-Blodgett films: effect of deposition velocity and pH

Multiple Langmuir-Blodgett (LB) films of arachidic acid were deposited on germanium (Ge) substrates from subphase solutions of 10(-4) M CdCl2 at different pH values and at different deposition speeds. Attenuated total reflectance infrared (ATR-IR) spectroscopy was used to obtain information on the molecular order and structure of these multilayer LB films. At pHs higher than the pKa of the fatty acid/cation system, transfers took place only during the downstroke, indicating X-type deposition. At pH = pKa and large deposition speeds, deposition partially failed during the downstroke, resulting in Z-type depositions. Analysis of the infrared spectra indicates that multiple LB films deposited only during the upstroke (Z-type) or during downstrokes (X-type) have a centrosymmetric structure typical of films deposited during the upstroke and downstroke, except for a slight decrease in molecular order and tilt angle as the pH increases (X-type). The centrosymmetric structure indicates that rearrangement of layers takes place between cycles. Experimental evidence of such rearrangement occurring in a fatty acid/divalent cation salt subphase is shown here, and rearrangement alternatives are discussed.