Fluorescein-Conjugated Bovine Albumin

Abstract

Fluorescein-bovine albumin conjugates have been prepared and found not to differ appreciably in size, shape, and homogeneity from the precursor, bovine serum albumin. Fluorescein has also been conjugated to rat plasma proteins. Their disappearance rates from the circulation of rats correspond with those obtained from the use of isotope labeling. Their sites of localization in rat tissues were shown to be in the cytoplasm but not in the nuclei of Kupffer cells, fixed macrophages, granulocytes, and proximal renal tubules. Adsorption to endothelium was a characteristic finding. Extracellular localizations were predominantly in the lumina of blood vessels and proximal renal tubules (but never in the lumina of collecting tubules), and the interstitial fluid of skeletal and cardiac muscle (but not that of glandular organs such as the adrenals, liver, and spleen). BAC absorption from the skin of rabbits requires days whereas sodium fluorescein absorption is measured in hours, attesting to the persistence of the colloidal state of BAC in vivo. Fluorescein conjugates have been used to visualize the transcapillary passage of circulating proteins in the mesenteric circulation of frogs and rats by direct microscopic observation and found to diffuse slowly in the manner predicted for plasma proteins. The normal cutaneous vessels of the rat are impermeable in the gross to the labeled proteins; second degree burn promptly increases the permeability of these vessels rendering the presence of the label detectable in the gross in the skin. The process of labeling does not render guinea pig albumin antigenic, although slight antigenicity results from labeling whole plasma protein. It is believed that sufficient biological evidence is presented to support the conclusion that fluorescein-conjugated plasma proteins, particularly albumin, behave in vivo like their native precursors.

Distribution of a Conjugate of 9-β-D-Arabinofuranosyladenine 5′-Monophosphate (ara-AMP) with Lactosaminated Albumin in Parenchymal and Sinusoidal Cells of Rat Liver

“…Conjugation with ara-AMP increased several fold the uptake of HSA by sinusoidal cells where the concentration of HSA-ara-AMP was ten times higher than in hepatocytes. This result is in agreement with the findings that after administration of denatured albumin tagged with a dye (25) or with fluorescein (26) or with 12sl| (27), the protein was observed only in sinusoidal cells. Also the uptake of ASOR and L3q-HSA by sinusoidal cells was increased following the coupling to ara-AMP which on the other hand did not decrease the penetration of these proteins into hepatocy¬ tes.…”

Studies on Fluorescent Antibody Staining

“…Similar in principle to the latter case is the coupling of proteins with aromatic isocyanates (1,(32)(33)(34). Studies on the reaction site between aromatic isocyanates and proteins have been reviewed by Coons and Kaplan (1).…”

“…The net loss of three positive charges on the protein molecule then results in a lowering of the isoelectric point and in alterations of electrophoretic mobility. More recently, Schiller et al (33) have studied the shift in isoelectric point when fluorescein isocyanate conjugates with bovine serum albumin.…”

Magnetic field remotely controlled selective biocatalysis

“…38 ) while papain is positively charged (the isoelectric point of papain is between 8.5 and 9.5, Sigma Papain P4762 datasheet) and FD-BSA has no overall charge (the isoelectric point of FD-BSA is 4.8; ref. 39 ). The interaction of proteins with polyelectrolyte brushes is a complex phenomenon 40 .…”