BIOANALYTICAL APPLICATIONS OF THERMAL LENS SPECTROMETRY

点击翻译按钮获取中文摘要

The main objective of this proposed research is to develop novel instruments and methods for the unique measurements of data which are currently unobtainable using existing techniques. The development is strategically based on the exploitation of the unique properties of the thermal lens effect. Specifically, the first, ultrasensitive, highly selective and rapid scanning multiwavelength thermal lens spectrophotometer (MWTL) and MWTL-circular dichroism spectropolarimeter (MWTL-CD) will be constructed. These instruments are capable of performing direct (i.e.; without pretreatment) and simultaneous determination (chemical and stereochemical) of multicomponent, small volume (mul) biological samples at very low concentrations. In one application, the developed MWTL-CD spectropolarimeter is used for the first chiral separation and determination of trans-7,8-dihydroxy-9,10-epoxy-7,8.9,10- tetrahydroxybenzo(a)pyrenes (BPDEs) -the type of investigation which is currently not feasible but is essential for the understanding of carcinogenic and mutagenic reactions between benzo(a)pyrene and DNA. Based on the use of these MWTL and MWTL-CD instruments, new methods will also be developed which will provide, for the first time: (1) an ultrasensitive and accurate kinetic method in which changes in the concentrations of the reactants and the products are simultaneously monitored and (2) the systematic structural investigation of interfacial water (i.e., vicinal water, a model for water adsorbed on surfaces of membranes). Reversed micelles will also be exploited to solubilize biological samples (i.e., proteins, nucleic acids) into nonpolar solvents which have relatively better thermo-optical properties than water. This solubilization process provides two main advantages: (1) the enhancement of the thermal lens signals of the compounds and (2) the capability to perform the measurements of these compounds in liquid water (i.e., water pools) at temperatures as low as -40 degrees C. Synergistic use of the developed apparatus and methods will then be performed for the kinetic determinations of enzymatic reactions in water pools of reversed micelles at room and cryogenic temperatures. The same kinetic measurements will also be performed when the enzymes and substrates are in a very thin film of water (i.e., vicinal water). Collectively results obtained from the proposed research will provide the necessary instruments and methods which scientists can easily use for the last but sensitive and selective determination of structures, concentrations, functions and processes of health related compounds. The knowledge obtained from the structural studies of BPDEs, the kinetic measurements of enzymatic reactions in a confined volume water will undoubtedly provide fundamentally important (but currently unavailable) information for such diverged fields as biochemistry, biology, chemistry, medicine and pharmaceutical sciences.