Biofunctionalization of zinc oxide nanowires for DNA sensory applications

We report on the biofunctionalization of zinc oxide nanowires for the attachment of DNA target molecules on the nanowire surface. With the organosilane glycidyloxypropyltrimethoxysilane acting as a bifunctional linker, amino-modified capture molecule oligonucleotides have been immobilized on the nanowire surface. The dye-marked DNA molecules were detected via fluorescence microscopy, and our results reveal a successful attachment of DNA capture molecules onto the nanowire surface. The electrical field effect induced by the negatively charged attached DNA molecules should be able to control the electrical properties of the nanowires and gives way to a ZnO nanowire-based biosensing device

Speciation, Luminescence, and Alkaline Fluorescence Quenching of 4-(2-methylbutyl)aminodipicolinic acid (H2MEBADPA)

4-(2-Methylbutyl)aminodipicolinic acid (H2MEBADPA) has been synthesized and fully characterized in terms of aqueous phase protonation constants (pKa\u27s) and photophysical measurements. The pKa\u27s were determined by spectrophotometric titrations, utilizing a fully sealed titration system. Photophysical measurements consisted of room temperature fluorescence and frozen solution phosphorescence as well as quantum yield determinations at various pH, which showed that only fully deprotonated MEBADPA2– is appreciably emissive. The fluorescence of MEBADPA2– has been determined to be quenched by hydroxide and methoxide anions, most likely through base-catalyzed excited-state tautomerism or proton transfer. This quenching phenomenon has been quantitatively explored through steady-state and time-resolved fluorescence measurements. Utilizing the determined pKas and quenching constants, the fluorescent intensity of MEBADPA2– has been successfully modeled as a function of pH

Diol esters - a family of potential plant growth regulators

Rice bran wax was found to contain 1, 3-propane diol mono- and diesters of palmitic, stearic, oleic and linolenic acids. The unsaturated esters (especially diesters) are found to be eminently active in the biological growth of rice and wheat seedlings in laboratory tests and under field conditions. They are able to induce appreciable increase in root length, fresh and dry weight, chlorophyll content and rate of photosynthesis in seedlings/plants and also yield of rice grains in the field. An extract of alfalfa revealed the presence of another family of diol esters, namely, 2-methyl 1, 4-butane diol esters of unsaturated acids which are at least as good as the 1, 3-propane diol esters in the plant growth regulating activities. Therefore, the plant growth regulating effect of alfalfa extract attributed to triacontanol could be due to the presence of diol esters as well. The natural occurrence of hitherto unreported diol esters and more importantly their plant growth regulating activities are now described

Drop drying on surfaces determines chemical reactivity - the specific case of immobilization of oligonucleotides on microarrays

BACKGROUND: Drop drying is a key factor in a wide range of technical applications, including spotted microarrays. The applied nL liquid volume provides specific reaction conditions for the immobilization of probe molecules to a chemically modified surface. RESULTS: We investigated the influence of nL and μL liquid drop volumes on the process of probe immobilization and compare the results obtained to the situation in liquid solution. In our data, we observe a strong relationship between drop drying effects on immobilization and surface chemistry. In this work, we present results on the immobilization of dye labeled 20mer oligonucleotides with and without an activating 5'-aminoheptyl linker onto a 2D epoxysilane and a 3D NHS activated hydrogel surface. CONCLUSIONS: Our experiments identified two basic processes determining immobilization. First, the rate of drop drying that depends on the drop volume and the ambient relative humidity. Oligonucleotides in a dried spot react unspecifically with the surface and long reaction times are needed. 3D hydrogel surfaces allow for immobilization in a liquid environment under diffusive conditions. Here, oligonucleotide immobilization is much faster and a specific reaction with the reactive linker group is observed. Second, the effect of increasing probe concentration as a result of drop drying. On a 3D hydrogel, the increasing concentration of probe molecules in nL spotting volumes accelerates immobilization dramatically. In case of μL volumes, immobilization depends on whether the drop is allowed to dry completely. At non-drying conditions, very limited immobilization is observed due to the low oligonucleotide concentration used in microarray spotting solutions. The results of our study provide a general guideline for microarray assay development. They allow for the initial definition and further optimization of reaction conditions for the immobilization of oligonucleotides and other probe molecule classes to different surfaces in dependence of the applied spotting and reaction volume