Ultraviolet and visible light spectrophotometric approach to blood typing: objective analysis by agglutination index.

BACKGROUND: A new blood typing technology based on ultraviolet (UV) and visible light spectroscopy (UV/visible spectroscopy) has been developed. Blood groups and types are determined by quantifying reproducible changes in the UV and visible light spectra of blood in the presence of agglutinating antibodies. STUDY DESIGN AND METHODS: Samples of red cells in the presence and absence of agglutinating antibodies were examined by UV/visible spectroscopy. Blood groups and types were determined by comparing the optical density spectra obtained between 665 and 1000 nm. These comparisons generate numbers (agglutination index) ranging from 0 to 100, with smaller numbers corresponding to lack of agglutination and larger numbers corresponding to agglutination. RESULTS: The optical density of agglutinated blood is dramatically different from that of unagglutinated blood. The agglutination index derived from the relative slopes of the spectra is an objective indicator of agglutination strength. An agglutination index greater than 17 consistently and accurately established blood group- and type-specific agglutination. CONCLUSION: The method accurately predicted A, B, and O blood groups, and D type in over 275 samples. Scattering theory-based calculations of relative volumes of red cells before and after agglutination show a direct correlation with the agglutination index and provide the theoretical basis of the analysis. This quantitative technique is reproducible and has the potential for automation.

Interaction of brain-type creatine kinase with its transition state analog: kinetics of inhibition and conformational changes.

The effects of components of the transition state analog (creatine, MgADP, planar anion) on the kinetics and conformation of creatine kinase isozyme BB from monkey brain was studied. From analysis of the reaction time course using the pH stat assay, it was shown that during accumulation of the reaction products (ADP and creatine phosphate), among several anions added, nitrate proved the most effective in inhibiting catalytic activity. Maximum inhibition (77%) was achieved with 50 mM nitrate. The Km for ATP was 0.48 mM and in the presence of 2.5 mM nitrate, 2.2 mM; for ATP in the presence of the dead-end complex, creatine and ADP, the apparent Km was 2.0 mM and the Ki was 0.16 mM; in the presence of the transition state analog, MgADP + NO3- + creatine, the Ki was estimated to be 0.04 mM. Ultraviolet difference spectra of creatine kinase revealed significant differences only in the presence of the complete mixture of the components of the transition state analog. Comparison of gel filtration elution profiles for creatine kinase in the absence and presence of the complete mixture of components of the transition state analog did not reveal any differences in elution volume. Addition of components of the transition state analog to creatine kinase resulted in only a marginal change in intrinsic fluorescence. The presence of the components of the transition state analog increased the rate of reactivity of the enzyme with trinitrobenzenesulfonic acid from k = 6.06 +/- 0.05 M-1 min-1 to 6.96 +/- 0.11 M-1 min-1.(ABSTRACT TRUNCATED AT 250 WORDS)