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R Lovrien

Publications and source records attributed to R Lovrien.

16 recordsLinked to original sources
PubMed1998

Lectin coprecipitative isolation from crudes by Little Rock Orange ligand.

Matrix ligands are intended for upstream use with dilute crudes on a large scale, splitting out sought-for proteins by coprecipitating them as dense, protected aggregates. Matrix ligand coprecipitation is rapidly, quantitatively reversible, by pH shifting and trapping matrix ligands on ion exchange resin, releasing the sought-for protein. Four lectins, wheat germ agglutinin, peanut lectin, concanavalin A, and Phaseolus vulgaris (red kidney bean) lectins, were coprecipitated from crude extracts, 0.05 to 0.4% crude protein, in a single step using Little Rock Orange matrix ligand. All were compared in specific activities (erythrocyte agglutination) and in SDS-PAGE analysis with the four corresponding commercial lectins purified by affinity chromatography. All four matrix-coprecipitated ligands were specifically active within range of the corresponding vendor (Sigma Co.) affinity chromatography-purified lectins. The matrix ligand coprecipitative technique requires optimization of ligand-protein (crude) ratios, denoted y, and determination of suitable pH ranges for coprecipitation relative to lectin isoelectric pH. These parameters control electrostatic ion pair association: ligand head anion binding to cationic target proteins. The coprecipitative and protective powers of new ligands like Little Rock Orange, their ability to scavenge sought-for lectins from dilute crudes, depend on ligand organic tail-tail association. After the strong anion heads of ligands bind to cationic proteins, their organic tails stack and draw the ligand-protein complexes together as aggregated coprecipitates.

Chemical Precipitation↗
PubMed1998

1-Anilino-8-naphthalene sulfonate anion-protein binding depends primarily on ion pair formation.

The ANS- (1-anilino-8-naphthalene sulfonate) anion is strongly, dominantly bound to cationic groups of water-soluble proteins and polyamino acids through ion pair formation. This mode of ANS- binding, broad and pH dependent, is expressed by the quite rigorous stoichiometry of ANS- bound with respect to the available summed number of H+ titrated lysine, histidine, and arginine groups. By titration calorimetry, the integral or overall enthalpies of ANS- binding to four proteins, bovine serum albumin, lysozyme, papain, and protease omega, were arithmetic sums of individual ANS(-)-polyamino acid sidechain binding enthalpies (polyhistidine, polyarginine, polylysine), weighted by numbers of such cationic groups of each protein (additivity of binding enthalpies). ANS- binding energetics to both classes of macromolecules, cationic proteins and synthetic cationic polyamino acids, is reinforced by the organic moiety (anilinonaphthalene) of ANS-. In a much narrower range of binding, where ANS- is sometimes assumed to act as a hydrophobic probe, ANS- may become fluorescent. However, the broad overall range is sharply dependent on electrostatic, ion pair formation, where the organic sulfonate group is the major determinant of binding.

Anilino Naphthalenesulfonates↗
PubMed1997

Three phase partitioning: concentration and purification of proteins.

Three phase partitioning (TPP) uses t-butanol and ammonium sulfate to precipitate enzymes and proteins from aqueous solutions. The method is useful both upstream with crude samples and downstream where a scaleable simple step is needed. About 25 enzymes and proteins have been isolated by various laboratories using TPP-t-butanol. The relation of t-butanol used in TPP, with n-butanol used as an extraction agent from Morton's work, is reviewed. Some t-butanol appears bound to TPP-precipitated proteins which are actually protein-t-butanol coprecipitates. They float above denser aqueous salts because bound t-butanol increases their buoyancy, similar to the behavior of many lipoproteins. On redissolving TPP-precipitated enzymes, total and specific activities usually are regained and sometimes increased. Sulfate ion-in large concentrations-likely exerts itself through its kosmotropic action as in conventional salting out. t-Butanol likewise appears to be a kosmotrope and crowding agent at room temperature or above, whereas C1 and C2 cosolvents (e.g., ethanol) do not so behave except at near or below zero temperatures. However, kosmotropy is not the entire origin of TPP, nor probably of conventional salting out. Electrostatic forces, capacity to force protein conformation tightening and protein hydration shifts, also contribute. Electrostatic forces, and the tendency for salt ions to bind and tighten protein molecule conformation, are indicated by the sharp pH dependency of both conventional salting out and TPP, around pH regions where proteins undergo conformation changes. Sulfate anion is densely-perhaps extraordinarily-hydrated, adding much to its effective size, and therefore it has a tendency to crowd or exclude proteins, when sulfate concentrations are in the 0.5 to 3 M range.

Chemical Precipitation↗
PubMed1977

Quantitative aspects of phenyl substituted alcohol and ether bacteriostatic interaction with Escherichia coli B/5.

It is well established that compounds of the class phenylalkane alcohols and ethers exert their antimicrobial action on the bacterial envelope--probably on the membrane. However, the overall stoichiometry, the number of molecules bound vs those merely added per cell, and the kinds of equilibria involved (site binding vs equipartitioning) are not clear. This work examines antimicrobial action on E. coli B/5 with eight such compounds. Directly determined binding data, plate counting viabilities, radiorespirometry, and microcalorimetry of glucose utilization were evaluated. The compounds mostly bind by simply equipartitioning, up to some threshold level, short of kill. That level depends sharply on the number of alkane carbons in the phenyl alkane derivative, but not on the precise structure. Past the threshold, bacteriostatic action is sudden and complete, probably reflecting cooperative behaviour in the cell envelope. The amount of bound compound at the threshold level is only about 0.5 to 3% of the weight of the bacterial envelope hydrocarbon, when bacteriostasis occurs. There is an unexpectedly small dependence on cell concentration. The principal governors on where the monooxygen phenylalkanes kill cells seems to be merely their concentration or chemical potential, the number of aliphatic carbons, and the binding mechanism. Because of the cell concentration independence, the cells act as if they constituted a second phase, relative to the solution. Results from the microcalorimetric method for assay of bacteriostasis correlate well with those from plate counting or viability assays.

Calorimetry↗
PubMed1975

Stoichiometry of compounds bound to human erythrocytes in relation to morphology.

Most work on human erythrocyte interaction with drugs and other compounds has been reported on the basis of total concentrations. Total concentrations alone do not reveal numbers of molecules bound per cell, v. This paper emphasizes determination of v and of binding isotherms, in conjunction with changes in cell morphologies and in hypotonic shock behavior as v is varied. Four drugs and five other compounds were studied, with fresh erythrocytes. The principal findings are: (1) the intact erythrocyte engages in two kinds of binding mechanisms, statistical binding and cooperative binding, depending on the compound. In the case of a detergent, dodecylbenzene sulfonate, the binding is nearly quantitative. (2) The compounds often induce considerable protection against hypotonic hemolysis. However, the binding levels at which maximum protection occurs are rather close to the levels, vL, that occur upon complete conversion to the first distorted morphology. Therefore, the maximally protected erythrocyte may be a distorted erythrocyte. (3) The value n is the apparent total number of sites from Scatchard plotting for compounds which bind in a statistical manner. Levels vp and vw characterize maxima in cooperative binding behavior, also from Scatchard plotting of the data. Despite the wide diversity of over-all levels at which compounds exert their effects, the critical binding levels of and numbers of sites fall into a narrow range:n, vL, vP, and vw are all between 1 and 8 times 10-7 molecules or sites per cell. Most of our data, and that from some other laboratories, indicate that about 2 plus and minus 1 times 10-7 sites per erythrocyte are available for compound binding by the intact cell. Beyond that level, the cell in suspension almost always will be forced into the first obvious morphology change, as seen by phase contrast microscopy. (4) Once stoichiometries are established, the total binding capacity of erythrocytes for such compounds, in blood, can be estimated. An intruding organic molecule would encounter about 6 times as many plasma albumin sites as erythrocyte sites, if the plasma albumin sites were free. However, because albumin in vivo usually forms a complex with one to two fatty acids, the erythrocyte itself is rather likely to act as a transport particle for such compounds.

Binding Sites↗
PubMedDate not supplied

Coprecipitation of proteins with matrix ligands: scaleable protein isolation.

Matrix ligands are agents for isolating proteins out of dilute crudes by coprecipitating proteins. The ligands have a strong anion sulfonate head which initiates binding to proteins having a positive net charge, ZH+ approximately 5-20. Initial binding tightens protein conformation and starts to squeeze water from conformationally motile proteins. The tails are stackable hydrophobic organic groups, azoaromatic dyes which draw protein-ligand complexes together. Proteins coprecipitate as guests, in the ligand host matrix. In addition to stacking, ligand tails displace water because of their bulk, and lower the average dielectric constant near charged groups, which reinforces the electrostatic component of binding. Matrix ligands protect proteins, scavenge them from dilute crudes (0.01-0.1 per cent protein), and densify coprecipitates. Detergent ions in low concentrations, 10(-4)-10(-5) M also sometimes serve as coprecipitating agents, entangling their tails but probably not stacking. Divalent metal ions, Zn++, sometimes are useful auxiliary agents. Preparative scaleability from crudes is demonstrated starting from 100-200 g of raw peanuts and raw pineapple to coprecipitate a lectin and bromelain enzyme respectively in 1-2 h with 80-90 per cent activity yields. Ligands are released from coprecipitates by shifting the pH and trapping the ligands with exchange resins. Protein conformation tightening in solution is seen by viscosity measurements.

Endopeptidases↗