Use of 8-anilino-1-naphthalenesulfonic acid in radioimmunoassay of triiodothyronine

Protection of human γD-crystallin protein from ultraviolet C-induced aggregation by ortho-vanillin

Cataract is known as one of the leading causes of vision impairment worldwide. While the detailed mechanism of cataratogenesis remains unclear, cataract is believed to be correlated with the aggregation and/or misfolding of human ocular lens proteins called crystallins. A 173-residue structural protein human γD-crystallin is a major γ-crystallin protein in the human eye lens and associated with the development of juvenile and mature-onset cataracts. This work is aimed at investigating the effect of a small molecule, e.g., ortho-vanillin, on human γD-crystallin aggregation upon exposure to ultraviolet-C irradiation. According to the findings of right-angle light scattering, transmission electron microscopy, and gel electrophoresis, ortho-vanillin was demonstrated to dose-dependently suppress ultraviolet-C-triggered aggregation of human γD-crystallin. Results from the synchronous fluorescence spectroscopy, tryptophan fluorescence quenching, and molecular docking studies revealed the structural change of γD-crystallin induced by the interaction/binding between ortho-vanillin and protein. We believe the outcome from this work may contribute to the development of potential therapeutics for cataract.

Homogeneous Enzyme Immunoassay for Triiodothyronine in Serum

Background: The concentration of triiodothyronine (T3) in human serum is extremely low and can be determined only by very sensitive methods. We developed a homogeneous enzyme immunoassay for T3 analysis in unextracted serum.

Methods: A T3 derivative was conjugated to the −SH groups of glycogen phosphorylase b (GPb) from rabbit muscle. Conjugation caused inhibition of enzyme activity, and the enzyme conjugate was reactivated upon binding of anti-T3 antibody. Activation was blocked by the presence of non-antibody-bound T3; this was the basis for the development of the homogeneous enzyme immunoassay for T3 by determining GPb activity fluorometrically.

Results: We used furosemide to block the interaction of T3 with serum proteins with T3-binding sites, avoiding any serum treatment step. T3 was measured in the range 0.3–8 μg/L. T3 values obtained by this assay correlated well with those obtained by a RIA (y = 0.97x − 0.07 μg/L; r = 0.96; n = 92). Within- and between-run imprecision (CV) was 5–9% for normal and high concentrations and 16–20% for low concentrations.

Conclusions: Chemical modification of GPb with a T3 derivative allows the development of a simple homogeneous enzyme immunoassay for T3 in unextracted serum.

A new radioimmunoassay of free thyroxine using 125I-labelled thyroxine-protein complex uninfluenced by albumin and thyroxine-binding globulin

We describe a double-antibody solid phase radioimmunoassay for free thyroxine (FT4) in serum with use of 125I-labelled thyroxine-human chorionic gonadotropin conjugate. Since the labelled conjugate does not bind to thyroxine binding globulin (TBG) and albumin because of its large molecular weight, the method is uninfluenced by TBG or albumin. The measurable range of FT4 in serum was 2.0 to 128 ng/l. The mean coefficients of variation within and between assays were 4.6-8.6% and 6.3-11.6%, respectively. The FT4 values determined by the proposed method correlated well with those determined by commercial radioimmunoassay in subjects with normal albumin concentration (r = 0.98). The FT4 concentrations in serum as determined by this method were 9 to 17 ng/l for healthy adult subjects; high for patients with hyperthyroidism; low for patients with hypothyroidism; and within normal limits for pregnant women, and patients with high or low concentrations of thyroxine-binding globulin.