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PubMed1962

Spectrophotometry of the periodic acid-Schiff reaction with pituitary hormones in vitro and in histological sections.

The spectral light absorption of the in vitro periodic acid-Schiff reactions of 4 purified pituitary hormones is described. The absorption spectra present a maximum between 560 and 565 mmicro. The color developed conforms with Beer's law for the ranges of concentration examined. The different hormones exhibit different chromogenicity per unit of biological activity: the color produced by 1 unit of FSH is equivalent to approximately 2 of TSH, 4 of LH, and 30 of ACTH. Microspectrophotometric measurements of the PAS-positive structures in histological sections of the human pituitary give absorption curves with shapes similar to those obtained in vitro, although quantitative differences exist. It is concluded that under the proper experimental conditions microspectra of the pituitary structures might, in the future, prove to give a quantitative measure of aldehyde groups generated from glycoprotein tropins by periodate oxidation.

Adrenocorticotropic Hormone↗
PubMed1975

Studies on the subsite structure of amylases. I. Interaction of glucoamylase with substrate and analogues studied by difference-spectrophotometry.

Studies were made on the ultraviolet difference-spectra of glucoamylase from Rhizopus niveus [EC 3.2.1.3] specifically produced by the substrate maltose and the inhibitors, glucose, glucono-1: 5-lactone (gluconolactone), methyl beta-D-glucoside, cellubiose, and cyclohexa-, and cyclohepta-amyloses. Of these, maltose and gluconolactone produced characteristic difference spectra with a trough near 300 nm. Based on studies with a model compound for a tryptophan residue, Ac-Trp, this trough was attributed to the effect of a negative charge upon the tryptophan residue. From the concentration dependency of the difference spectra, the dissociation constants of the complexes between the enzyme and maltose, glucose, and gluconolactone were evaluated to be 1.2 mM, 51 mM, and 1.5 mM, respectively. These values are in good agreement with the values of Km or K1 obtained from the steady-state kinetics. The difference-spectrophotometric data suggested that referring to the values of subsite affinities of glucoamylase, maltose, and gluconolactone occupy mainly Subsite 1, where the non-reducing-end glucose residue of a substrate is bound in a productive form and that a tryptophan residue with shows a trough near 300 nm in difference spectra is located in this subsite.

Amino Acids↗
PubMed1993

Identification of rigid gas permeable contact lens materials by means of ultraviolet-visible spectrophotometry.

Identification of the material used in an unknown rigid gas permeable (RGP) contact lens is not easily achieved by either manufacturer or contact lens practitioner. It is proposed that the spectral transmittance characteristics in the ultraviolet and visible regions can characterize a material sufficiently to identify it. The characteristics of some materials are discussed and a short double blind trial of the identification system reported. Ultraviolet-visible spectrophotometers are widely available and can be relatively inexpensive. The method is proposed as being a practical reality.

Contact Lenses↗