Metal complexes as mediator-titrants for electrochemical studies of biological systems

Various redox-active metal complexes were evaluated electrochemically for stability, reversibility, and general utility as mediator-titrants in the 0 to + 1.0 V vs standard hydrogen electrode range. Those complexes which were evaluated and appear to be useful in potentiostatic or potentiometric techniques are Ru(bpy)3(CIO4)2, Ru(bpy)2(im)2, Os(bpy)3(NO3)2, K2Fe(phen)(CN)4, Co(phen)3Cl2, and Co(terpy)2Cl2.

Synthesis of photoaffinity analogs of progesterone

A photoaffinity analog of progesterone, 11 alpha-diazoacetate progesterone, has been synthesized by a two step procedure. This has been made possible by a single reaction combining both esterification and diazotization. Numerous diazoacetate analogs of progesterone can be synthesized using these simple reaction conditions. Radioactive analogs can be produced that transfer the isotope covalently to the site of protein modification upon photolysis.

Electrochemical investigation of hapten-antibody interactions by differential pulse polarography

The binding of electroactively labeled estriol with estrogen-specific antibody and its subsequent displacement by unlabeled estriol have been monitored by differential pulse polarography. Estriol was found to be electro-inactive in the potential range -200 mV to -1000 mV vs a silver/silver chloride electrode. Estriol labeled in the 2 and 4 position with nitro groups was electroactive, giving two reduction waves at -422 mV and -481 mV vs a silver/silver chloride electrode. The peak current was linear with concentration over the range 60 micrograms/L to 3.7 mg/L. The addition of aliquots of estrogen-specific antibody reduced the peak current proportionately, indicating the binding of ligand to specific antibody. Subsequent addition of unlabeled estriol produced incremental increases in peak reduction current, indicating competitive and reversible binding of the two ligands for the antibody. Separation of bound from free labeled hapten was not necessary because reduction of the antibody-bound labeled estriol is attenuated at the electrode.

Enzyme immunoassay with flow-amperometric detection of NADH

Using phenytoin as a model analyte, we demonstrate that an enzyme-coupled immunoassay based on flow-injection analysis and amperometric detection of NADH is both feasible and practical. Good agreement with a routine clinical laboratory procedure for phenytoin was obtained for patients' serum samples. The electrode must be protected to prevent fouling by proteins in the analytical sample. The optimum detection range for NADH was at 0.01 of the concentrations of NADH generated during the several minutes required for each analysis. This suggests that the electrochemical technique should be extendable to the determination of species at concentrations in the microgram per liter range.

Enzyme immunoassay with flow-amperometric detection of NADH

Using phenytoin as a model analyte, we demonstrate that an enzyme-coupled immunoassay based on flow-injection analysis and amperometric detection of NADH is both feasible and practical. Good agreement with a routine clinical laboratory procedure for phenytoin was obtained for patients' serum samples. The electrode must be protected to prevent fouling by proteins in the analytical sample. The optimum detection range for NADH was at 0.01 of the concentrations of NADH generated during the several minutes required for each analysis. This suggests that the electrochemical technique should be extendable to the determination of species at concentrations in the microgram per liter range.

Electrochemical investigation of hapten-antibody interactions by differential pulse polarography

The binding of electroactively labeled estriol with estrogen-specific antibody and its subsequent displacement by unlabeled estriol have been monitored by differential pulse polarography. Estriol was found to be electro-inactive in the potential range -200 mV to -1000 mV vs a silver/silver chloride electrode. Estriol labeled in the 2 and 4 position with nitro groups was electroactive, giving two reduction waves at -422 mV and -481 mV vs a silver/silver chloride electrode. The peak current was linear with concentration over the range 60 micrograms/L to 3.7 mg/L. The addition of aliquots of estrogen-specific antibody reduced the peak current proportionately, indicating the binding of ligand to specific antibody. Subsequent addition of unlabeled estriol produced incremental increases in peak reduction current, indicating competitive and reversible binding of the two ligands for the antibody. Separation of bound from free labeled hapten was not necessary because reduction of the antibody-bound labeled estriol is attenuated at the electrode.

The binding of spin-labeled propranolol and spin-labeled progesterone by orosomucoid

The binding of the spin-labeled propranolol and spin-labeled progesterone to human orosomucoid has been studied as a function of temperature by electron spin resonance (ESR) techniques. At 20 degrees C the association constants are 1.9 x 10(6) and 4.9 x 10(5) M-1, respectively. In each case, the binding is competitive with unlabeled ligand. Above about 50 degrees C the apparent association constant for both ligands decreases rapidly with increasing temperature. This is due to thermal denaturation of the orosomucoid, as was shown independently by ultraviolet absorption spectroscopy and differential scanning calorimetry. Below the denaturation region the number of binding sites per orosomucoid molecule remains constant at approx. 1. Examination of the thermodynamic parameters shows the progesterone binding at 37 degrees C to be essentially enthalpically driven, while the propranolol binding at 37 degrees C has a substantial entropic component.

The preparation of orosomucoid from nephrotic urine

A gel chromatographic and ion exchange procedure is described for the preparation of orosomucoid from nephrotic urine. The removal of endogenous lipid and glycosaminoglycan than yields a highly homogeneous preparation. Aggregates are formed at ambient temperatures and as a result of lyophilisation of ultrafiltration.

A microcapillary assay (MASS) for macrophage migration inhibition factor

A technically simple microassay for macrophage migration inhibition studies is described. Using simple 0.08 ml of test solution per assay, meaningful statistical analysis via multiple replicates is possible. A novel feature is that test solutions may be stored frozen in the test well until the indicating macrophages are ready for use. The assay was used to demonstrate that MIF, derived from the human lymphoid cell line RPMI 1788, eluted from Sephadex G-75 in the molecular weight range of 13,000--25,000.

Immunoassay by differential pulse polarography

An immunological method based on labeling an antigen with an electroactive group detectable by differential pulse polarography has been demonstrated. Estriol labeled with mercuric acetate is electroactive, giving a reduction wave at -300 millivolts versus a standard calomel electrode. Addition of estriol antibody to 4-mercuric acetate estriol diminishes the peak current as a result of the antigen-antibody binding reaction. Separation of free-labeled estriol from antibody-bound-labeled antigen is unnecessary. The method is potentially useful as an analytical immunological technique.

Simultation of gradient and band propagation in the centrifuge

A technique is developed for simulating the behavior of both the gradient-forming solute and macromolecular bands in a centrifuge. The change with time of the density gradient due to diffusion and sedimentation of the gradient-forming solute is calculated by a finite difference method, making use of the results of earlier work on the theory of the equilibrium density gradient. Using a perturbation technique, the concentration profiles of dilute bands of macromolecules are then calculated as they sediment and diffuse through the varying supporting gradient. Results of the stimulaion techniques are compared with experiment.

Effect of polymerized orosomucoid on some strains of influenza virus

1. Polymers of orosomucoid were produced in two molecular shapes, filamentous (;chain') and spherical (;ball'), by heating the sodium salt of the monomer in either water or high concentrations of sodium chloride. An ;intermediate' state containing both shapes in various proportions was found in preparations obtained by polymerizing orosomucoid in intermediate concentrations of sodium chloride. 2. The filamentous form of polymer was found to inhibit strongly the haemagglutination of some (;sensitive') strains but not of other (;insensitive') strains of influenza virus; the ;intermediate' form feebly inhibited haemagglutination by ;sensitive' strains. 3. The filamentous form agglutinated both ;sensitive' and ;insensitive' strains of virus; the other forms of polymer did not. It also inhibited multiplication of both ;sensitive' and ;insensitive' strains when inoculated into embryonated and de-embryonated eggs. 4. The ;intermediate' and spherical forms of the polymer had no effect on the virus multiplication. 5. Polymers of orosomucoid from which neuraminic acid had been split off had no detectable effect on influenza viruses.

The thermal polymerization of orosomucoid

1. Orosomucoid was prepared from the urine of a nephrotic patient and polymerized by heating it in a range of salt concentrations at pH4.1. 2. Heating at low ionic strengths produced a ;chain' polymer of indefinite length but having the same width as the diameter of the monomer (5.0nm.). Similar treatment in high ionic strengths also produced a spherical (;ball') polymer of limited diameter (14.8nm.). 3. The size and shape of both polymers were determined from ultra-centrifuge, gel-filtration and electron-microscope results. The results suggest that eight monomer units condense to form the ball polymer. 4. Heating orosomucoid at pH1.8 hydrolysed the N-acetylneuraminic acid off the molecule; only chains could then be formed, even in high ionic strengths. 5. Both polymers were stable under normal conditions but could be depolymerized in 3m-guanidine hydrochloride. The monomer could be repolymerized on heating: the ;chain monomer' only formed chains at all ionic strengths, but the ;ball monomer' was indistinguishable from the original monomer in its immunological properties and polymerization reaction.