Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An efficient method for labeling and visualizing phospholipids at the ultrastructural level is described. Biotin was coupled to the amines of appropriate phospholipids via the N-hydroxysuccinimide ester. The biotinylated lipid could be specifically labeled by ferritin-avidin conjugates and detected by transmission electron microscopy. The lipid derivatives were analyzed and evaluated in terms of their resemblance to the original lipid. Although differing in some aspects from the parent lipid molecules, the biotinyl derivatives still retain the basic characteristics of lipids vis-a-vis their orientation and position in the membrane bilayer. The latter property renders the biotinylated lipid qualitatively suitable for tracing the fate of the lipid component(s) of liposomes during their interaction with biological membranes of various cell types. Using this system, we propose that the extent and pattern of the liposome-cell interaction depends, at least in part, on the cell type employed. This observation may be due to intrinsic variations in cell surface structure and properties relative to those of the liposome.
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PMID:On the mode of liposome-cell interactions. Biotin-conjugated lipids as ultrastructural probes. 42 Aug 28

Insulin was modified with d-biotin-N-hydroxysuccinimide ester in dimethylformamide. Mono-, di-, and triacylated insulins were separated by preparative isoelectric focusing. Monoacylated derivatives (isoelectric point 5.1) were fractionated twice on DEAE-cellulose to yield pure N epsilonB29-biotinylinsulin. The structure of the product was established by amino acid analysis before and after deamination. N epsilonB29-biotinylinsulin had biological activity indistinguishable from insulin on glucose oxidation and lipid synthesis assays using isolated rat epididymal fat cells. Complexes of N epsilonB29-biotinylinsulin with avidin, having essentially all but one binding site filled with biotin, were prepared in order to obtain a 1:1 insulin:avidin ration. The elicited identical maximal biological responses, but showed a potency decreased to 5% of that of insulin. Such complexes conjugated with ferritin will provide a useful tool in the development of electron microscopic stains of insulin receptors.
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PMID:N epsilonB29-(+)-biotinylinsulin and its complexes with avidin. Synthesis and biological activity. 62 Nov 98

To expand the electron microscopist's options in localization and visualization, a new and general staining technique has been tested. The avidin-biotin complex serves as a coupling between the electron-dense marker, ferritin, and points of interest in biological samples. When specific cellular components are tagged with biotin, those components may be visualized with ferritin-linked avidin. Because of the remarkably strong affinity of avidin and biotin (characterized by an association constant of 10(15) M(-1)), the staining is rapid and stable. The preparation of ferritin-avidin conjugate is described, and examples are presented of the application of this complex to biotin-tagged membranes. The ghosts of Acholeplasma laidlawii have been treated with biotinyl-N-hydroxysuccinimide ester to label protein amino groups. Erythrocyte membrane oligosaccharides have been oxidized by periodate or by galactose oxidase, and the resulting aldehydes labeled with biotin hydrazide. The avidin-biotin complex in electron microscopy seems especially appropriate for seqential staining procedures, as well as for visualization of reaction sites of biotin-labeled, low-molecular-weight reagents.
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PMID:Use of the avidin-biotin complex for specific staining of biological membranes in electron microscopy. 413 15

A mild and efficient procedure for conjugating rabbit Fab' and horseradish peroxidase using a maleimide compound was developed. The enzyme was treated with N-hydroxysuccinimide ester of N-(4-carboxycyclohexylmethyl) maleimide to introduce maleimide groups. Then, the maleimide-enzyme was allowed to react with thiol groups of Fab', and the conjugate formed was separated from unreacted components by gel filtration with Ultrogel AcA 44. In the peak fraction of the separated conjugate, 98% of peroxidase was associated with Fab' and 90% of antibodies was associated with peroxidase. The recoveries in the conjugate of peroxidase and Fab' incubated for conjugation were 65-74%. The conjugate formed appeared to be largely monomeric. Both the enzyme activity and antigen-binding activity of Fab' were fairly well preserved in the conjugate. The cross-link formed was stable at 4 degrees C at least 6 months. Use of the conjugates obtained by this method gave greater sensitivity in sandwich enzyme immunoassay for human ferritin and human thyroid-stimulating hormone than conjugates prepared by the periodate method. The conjugation using N-hydroxysuccinimide ester of m-maleimidobenzoic acid provided a similar monomeric preparation but was less efficient.
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PMID:Mild and efficient conjugation of rabbit Fab' and horseradish peroxidase using a maleimide compound and its use for enzyme immunoassay. 675 1

Specific binding sites for [Asp1,Ile5]angiotensin II (angiotensin) have been demonstrated in homogenates and subcellular fractions of aortic medial smooth muscle cells, but the localization of the angiotensin receptor responsible for contraction has not been determined [Devynck, M. A., & Meyer, P. (1976) Am. J. Med. 61, 758-767]. To establish the location of this receptor, we have prepared a membrane-impermeable analogue of angiotensin by acylating its N-terminal amino group with the N-hydroxysuccinimide ester of succinylated ferritin. This angiotensin-ferritin conjugate possessed the same intrinsic activity as angiotensin but was approximately 200 times less potent in inducing contraction in rabbit aortic strips. The stability of the conjugate was investigated, and approximately 5% of the contractile activity of the angiotensin-ferritin conjugate was attributable to low molecular weight components that were present before or after exposure to aortic strips. The time required for aortic strips to reach a plateau of contraction in response to angiotensin-ferritin was significantly longer than that required by free angiotensin to produce the same level of contraction. With enzymatically dispersed aortic smooth muscle cells, however, the time taken to produce contractions by both angiotensin and angiotensin-ferritin was indistinguishable. [Sar1,-Ala8]angiotensin II, a competitive inhibitor of angiotensin, completely suppressed contractions induced by angiotensin or angiotensin-ferritin in aortic strips or dispersed aortic smooth muscle cells. These results suggest that angiotensin need not directly penetrate the plasma membrane to cause contraction and imply that the angiotensin receptor responsible for initiating contraction of aortic smooth muscle cells is located on the plasma membrane.
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PMID:Biological activity of an angiotensin II--ferritin conjugate on rabbit aortic smooth muscle cells. 726 47

Antibodies conjugated with porphyrins and metalloporphyrins have a great potential for applications in fluorescence or phosphorescence immunoassays as well as in photodynamic therapy, radioimaging and internal radiation therapy of cancer. Here we describe how the new preactivated metalloporphyrin, palladium (II) coproporphyrin I-tetra-N-hydroxysuccinimide ester, can be covalently attached to mouse monoclonal and rabbit anti-human ferritin antibodies. The advantages of the proposed reagent over the previously reported carboxylic porphyrins coupled through carbodiimide activation are indicated. Conformational changes in antibodies caused by each of the two methods were assessed from their binding to the antigen (a probe for the antibody Fv domain) and anti-IgG antibodies probing the global conformation of the CH2 domain in the Fc fragment. Porphyrin coupling through carbodiimide activation resulted in a decrease in both functional activities of modified antibodies even at low levels of modification. In contrast, when the N-hydroxysuccinimide (NHS) derivative of porphyrin was used, enhancement of the antigen-binding affinity of porphyrin-antibody conjugates occurred due to an increase in the conformational mobility (flexibility) of the modified antibodies. The stimulatory effect of conjugation was maximal when one porphyrin molecule was coupled to an antibody molecule. Coupling of NHS-activated porphyrin at pH 7.4, 7.8 and pH 8.5 suggested that the high efficiency of the reaction at pH 8.5 could be attributed predominantly to the formation of antibody aggregates, only 50% of which were covalently cross-linked. The lowest percentage of aggregates in porphyrin-antibody conjugates was found at pH 7.4 and a molar reagent-to-protein ratio in the 10:1-40:1 range. Thus, the use of the NHS-activated carboxylic porphyrin provides a mild, simple and convenient procedure for preparing antibody conjugates with enhanced antigen-binding affinity.
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PMID:Modification of monoclonal and polyclonal IgG with palladium (II) coproporphyrin I: stimulatory and inhibitory functional effects induced by two different methods. 759 29

Metalloporphyrin-antibody conjugates provide a significant advantage over other types of conjugates in biomedical use for phosphorescence immunoassay, targeted immunotherapy, and internal imaging of malignant tumors. Monoclonal HSF102 antibody of mouse IgG2a subclass and monospecific rabbit IgG, both antibodies directed to human spleen ferritin, were modified with the new reagent Pd(II) coproporphyrin I tetra-N-hydroxysuccinimide ester. Functional study of the conjugates obtained revealed a 7- and 1.4-fold increase in the antigen binding activity for monoclonal HSF102 and monospecific IgG antibodies, respectively. For rabbit monospecific IgG, a concomitant increase in binding to anti-rabbit IgG antibodies directed to the epitopes of the CH2 domain in the Fc fragment was observed. In all cases, the maximum functional activation was found after conjugating one mole porphyrin per mole antibody. These results suggest that functional activation of the conjugates might be due to an increase in conformational flexibility of an antibody molecule after the modification. This increase in flexibility involves the Fab fragments and a pair of the CH2 domains in the Fc fragment and might be due to a significant charge shift (minus 5 charge units per modified amino group) that occurs after conjugation of an antibody with tetracarboxylic porphyrin.
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PMID:Functional activation of antibodies on modification with Pd(II) coproporphyrin I N-Hydroxysuccinimide ester. 936 Mar 5