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Biomedical subjects

H Grothe

Publications and source records attributed to H Grothe.

6 recordsLinked to original sources
PubMed2006

Theoretical study on the structure of the BrO hydrates.

The hydrates of bromine monoxide, BrO(H2O)n, n = 1-4, have been studied by means of ab initio calculations at the B3LYP/aug-cc-pVTZ level of theory. These systems could be formed in the troposphere and participate in chemical reactions involved in the depletion of ozone. Several conformations are obtained and discussed for each of the hydrates mentioned. Two rather different intermolecular interactions are found, namely, conventional hydrogen bonding and Br...O associations. In contrast with a more traditional point of view in which hydrogen bonds could be assumed as the preferential interaction for the formation of these complexes, it is the Br...O association which yields the most stable conformations. Equilibrium geometries, harmonic frequencies, and relative energies have been calculated for the bromine monoxide hydrates for the first time. The theoretical binding energies indicate that the stabilization of the hydrates increases with the number of water molecules added. Cooperative effects are suggested to play a significant role in this stabilization. An analysis of relevant properties depending on the electron density in the bond critical points of the Br...O associations has been done for the first time, showing characteristic features of this interaction in comparison with the hydrogen bonds formed.

Journal Article↗
PubMed2005

Optical constants of HNO3/H2O and H2SO4/HNO3/H2O at low temperatures in the infrared region.

The complex index of refraction of liquid HNO3/H2O and H2SO4/HNO3/H2O has been obtained at different temperatures and acid concentrations. FT-IR specular reflectance spectra were obtained for 30, 54, and 64 wt % aqueous HNO3 and for four different H2SO4/HNO3/H2O mixtures in the temperature region from 293 to 183 K. The complex index of refraction was obtained from the reflectance spectra with the Kramers-Kronig transformation. The optical constants of the binary and ternary mixtures vary with the acid concentration and the temperature. The results demonstrate that vibrational bands originating from the sulfate species are more sensitive to changes in temperature than the bands originating from vibrations in the nitrate species; only minor changes in the nitrate vibrational bands are observed as the temperature decreases below 248 K.

Journal Article↗
PubMed2003

Functional cellular assays with multiparametric silicon sensor chips.

Multiparametric silicon sensor chips mounted into biocompatible cell culture units have been used for investigations on cellular microphysiological patterns. Potentiometric, amperometric and impedimetric microsensors are combined on a common cell culture surface on the chip with an area of approximately 29 mm2. Extracellular acidification rates (with pH-sensitive field effect transistors, ISFETs), cellular oxygen consumption rates (with amperometric electrode structures) and cell morphological alterations (with impedimetric electrode structures, IDES) are monitored on single chips simultaneously for up to several days. The corresponding test device accommodates six of such sensor chips in parallel, provides electronic circuitry and maintains the required cell culture conditions (temperature, fluid perfusion system). Sensor data are transformed into quantitative information about microphysiologic conditions. The outcome of this transformation as well as reliability and sensitivity in detection of drug effects is discussed. This is the first report on multiparametric cell based assays with data obtained solely with integrated sensors on silicon chips. Those assays are required in different fields of application such as pharmaceutical drug screening, tumor chemosensitivity tests and environmental monitoring.

Acetaldehyde↗
PubMed2001

Multiparametric microsensor chips for screening applications.

The identification of drug targets for pharmaceutical screening can be greatly accelerated by gene databases and expression studies. The identification of leading compounds from growing libraries is realized by high throughput screening platforms. Subsequently, for optimization and validation of identified leading compounds studies of their functionality have to be carried out, and just these functionality tests are a limiting factor. A rigorous preselection of identified compounds by in vitro cellular screening is necessary prior to using the drug candidates for the further time consuming and expensive stage, e.g. in animal models. Our efforts are focused to the parallel development, adaptation and integration of different microelectronic sensors into miniaturized biochips for a multiparametric, functional on-line analysis of living cells in physiologically environments. Parallel and on-line acquisition of data related to different cellular targets is required for advanced stages of drug screening and for economizing animal tests.

Biocompatible Materials↗
PubMed1998

High-Resolution Infrared Fourier-Transform Spectroscopy and Rotational Constants of the nu4 Band of BrNO2.

For the first time, high-resolution infrared gas-phase absorption spectra of the BrNO2 molecule were recorded using a Fourier-transform spectrometer. In this paper, the nu4 bands of the 79BrNO2 and 81BrNO2 isotopomers around 1670 cm-1 are investigated. Although the spectra are highly congested, rotational and centrifugal distortion constants for the ground and v4 = 1 states of 79BrNO2 and 81BrNO2 were determined. The results show that BrNO2 is a planar molecule of C2nu symmetry and confirm predictions from a recent ab initio study. Copyright 1998 Academic Press.

Journal Article↗