PubMed Health⌕ Search

Biomedical subjects

N Ressler

Publications and source records attributed to N Ressler.

At least 19 recordsLinked to original sources
PubMed1993

A novel electrostatic approach to enzyme mechanisms: carbonic anhydrase as an example.

A novel electrostatic approach to the manner in which enzymes catalyze reactions is developed. In this development, the author's interpretations of, and additions to, the late K. Fajans' theory of electronic structure (referred to as the Quanticule theory of chemical binding) are presented. This theory is based upon electron densities, in analogy to density functional theory. It is used to derive formulations of molecular structure, (Fajans' formulations) which show the charges of the atomic components. These charges are shown to be reduced by polarization to what are commonly referred to as partial charges. These formulations relate to the exchange of charged atomic components during reactions. The relevance of the formulations to the catalytic activity of enzymes is illustrated with carbonic anhydrase. When viewed in terms of Fajans' formulations, the active site is seen to consist of an array of charged atoms. The positive and negative charges tend to alternate. When closely positioned, these charges provide a basis for drawing atomic components of the molecules, which are exchanged in a given reaction, into the new positions. The charges are shown to be related to the binding of substrates to the enzyme and the positioning of them so that they can interact, to the reaction itself, to an essential proton transfer, and to the dissociation of the product from the enzyme. This more extensive scope of electrostatic interactions provides a more simple view of the manner in which the catalysis is accomplished. Such catalysis is consistent with a number of other proposals about enzyme mechanisms, and appears to be applicable to a large majority of enzyme-catalyzed reactions.

Binding Sites↗
PubMed1985

Electronic aspects of serine protease catalysis.

A new electrostatic approach is applied to serine protease catalysis. It is is based upon the demonstration that the polarities, or partial charges, of the atomic components of the molecules involved in the reaction alternate in sign. When the atomic components of opposite polarities of the enzyme and substrate approach close to each other during the catalysis, the electrostatic interactions between them increase in intensity. These increasing interactions are related to the decrease in the energy barrier. When the serine protease--catalyzed reaction is followed from this perspective, it is shown to result in a marked simplification of the catalytic mechanism. A number of concerted proton transfers and electron density displacements around the active site are indicated. This approach is not inconsistent with other electrostatic methods, and is supported by independent partial charge calculations.

Asparagine↗
PubMed1976

Improved method for determining serum protein concentrations in the far ultraviolet.

We examined the feasibility of measuring absorbance in the far ultraviolet for serum protein determination with a medium-priced, double-beam spectrophotometer. The method has been simplified by using an automatic dilutor to dilute the serum, and a flow-through cell and recorder in conjunction with the spectrophotometer. Because it is only necessary to dilute the serum and determine its absorbance, the procedure is quite rapid. As compared to the biuret reaction, interferences from hemolysis have been about halved. Interferences owing to light scattering by turbid sera have also been appreciably decreased by use of an anionic detegent (sodium dodecyl sulfate) as a serum diluent. Comparisons of the present method to the biuret and Kjeldahl methods indicate that it is relatively accurate, and is practical for routine use.

Blood Proteins↗
PubMed1975

Computer-assisted diagnosis by a model-free system of direct data analysis.

The basis of the method of data analysis presented is, in the case of any diagnostic test, the automatic compilation of separate frequency distributions for each diagnostic classification. The distinction of different test results for different diseases (the correlation for which the tests are used) can thus be quantitatively monitored. This offers opportunities for more specific control of the accuracy of the data base. Measurements of relative frequencies obtained from the frequency distributions of individuals with and without a given disease can serve as a quantitative handle for the selection of the combination of tests, and for adjustments of individual parameters, which will maximize the discrimination. The usual cutoffs are not used. A data-processing system can serve for the direct incorporation of patient chart data (including test results), and for the automation of the analysis described, with pattern recognition or cluster-seeking techniques. The ability of this system of analysis to minimize some of the problems associated with methods utilizing mathematical models is discussed.

Diagnosis, Computer-Assisted↗
PubMed1970

Tissue-characteristic forms of glyceraldehyde 3-phosphate dehydrogenase.

Glyceraldehyde 3-phosphate dehydrogenase exists in two different forms in various human tissue preparations. One of them is exhibited, after starch-gel electrophoresis, by a rapidly migrating or ;fast' band and the other by a ;slow' band. The proportion of the total activity in each of the two forms is characteristic of the type of tissue. A particulate fraction, obtained after centrifugation of homogenates, inhibits the enzyme activity and tends to convert the slow band into a fast one. The conversion is reversible. The fast band can also be converted into the slow one by addition of NAD(+) or ADP, or by dialysis against saturated sodium chloride solution. Conversions occur with the purified enzyme as well as with crude homogenates. The relevance of these findings to previous investigations and to glycolytic control mechanisms are discussed.

Adenine Nucleotides↗