Applications of Surface Plasmon Resonance (SPR) to the Study of Diverse Protein-Ligand Interactions.

Functional characterization of enzymes/proteins requires determination of the binding affinity of small molecules or other biomolecules with the target proteins. Several available techniques, such as proteomics and drug discovery strategies, require a precise and high-throughput assay for rapid and reliable screening of potential candidates for further testing. Surface plasmon resonance (SPR), a well-established label-free technique, directly measures biomolecular affinities. SPR assays require immobilization of one interacting component (ligand) on a conductive metal (mostly gold or silver) and a continuous flow of solution containing potential binding partner (analyte) across the surface. The SPR phenomenon occurs when polarized light excites the electrons at the interface of the metal and the dielectric medium to generate electromagnetic waves that propagate parallel to the surface. Changes in the refractive index due to interaction between the ligand and analyte are measured by detecting the reflected light, providing real-time data on kinetics and specificity. A prominent use of SPR is identifying compounds in crude plant extracts that bind to specific molecules. Procedures that utilize SPR are becoming increasingly applicable outside the laboratory setting, and SPR imaging and localized SPR (LSPR) are cheaper and more portable alternative for in situ detection of plant or mammalian pathogens and drug discovery studies. LSPR, in particular, has the advantage of direct attachment to test tissues in live-plant studies. Here, we describe three protocols utilizing SPR-based assays for precise analysis of protein-ligand interactions. © 2024 Wiley Periodicals LLC. Basic Protocol 1: SPR comparison of binding affinities of viral reverse transcriptase polymorphisms Basic Protocol 2: SPR screening of crude plant extract for protein-binding agents Basic Protocol 3: Localized SPR-based antigen detection using antibody-conjugated gold nanoparticles.

Psychosocial crisis in diabetic renal failure.

Twenty-nine diabetic renal failure patients suffered a psychosocial crisis at the time when chronic dialysis or renal transplantation was required. These patients could be classified into groups as to the impact of the crisis in terms of participation in life-support therapy. Group 1 consisted of potentially lethal mechanism (9 patients): discontinued dialysis (5); refused to start dialysis (3); overt act to cause personal harm (1). Group 2 contained probably nonlethal mechanism (11 patients): threatened to discontinue dialysis or to never start dialysis if not given a chance for a transplant (5); threatened to discontinue dialysis or to never start dialysis (5); threatened to cause personal harm (1). Group 3 consisted of a combination of mechanisms (9 patients): with drug abuse (4); without drug abuse (5). Important similarities between the groups were easier to document than were subtle differences in the kinds of options in family and employment relationships; in the degree of objective and subjective handicap due to impaired vision; in the level of expectation and/or disappointment following renal transplantation; and in the capacity to cope with changing personal relationships produced by the complications of diabetes.

Immunological: reactions involving leukocytes: III. Agranulocytosis induced by antithyroid drugs.

A method has previously been described which detected xenogeneic and allogeneic antibodies to human granulocytes by their inhibition of the normal phagocytosis-associated hexose monophosphate shunt (HMS) activity. This method was used to study three patients with acute agranulocytosis secondary to antithyroid drug administration. Two patients with methimazole and one patient with propylthiouracil induced agranulocytosis were studied. Serum samples from each of these three patients taken during the acute phase of agranulocytosis had inhibitory effects on phagocytosis-associated HMS activity in leukocytes from both normal donors and the patients after their full recovery from agranulocytosis. IgM but not IgG prepared from acute sera in two patients was also inhibitory. Disruption of IgM disulfide bonds by dithiothreitol destroyed its inhibitory activity. The possibility of drug-dependent immune destruction of leukocytes in these patients is discussed.