Adsorption of pepsin by aluminum hydroxide II: Pepsin inactivation

Pepsin adsorbed on gibbsite or boehmite, non-acid-reactive forms of aluminum hydroxide, had a significantly lower activity than pepsin in solution. IR and desorbed pepsin activity studies showed that the reduced activity of adsorbed pepsin was not due to denaturation of pepsin on adsorption. Steric occlusion of the active site, following pepsin adsorption, was responsible for the lower activity of pepsin adsorbed on gibbsite. The porous morphology of boehmite caused diffusional resistance and steric exclusion, contributing to the decreased activity of adsorbed pepsin. The specific inactivation of pepsin by adsorption on aluminum hydroxide may be important in ulcer therapy.

Retention model for proteins in reversed-phase liquid chromatography

This paper presents a retention model for proteins on an reversed-phase chromatography support in which retention is a function of the number (Z) of solvent molecules required to displace the solute from the surface. An equation is derived that relates the capacity factor of a protein to the displacing agent concentration and the stoichiometry of solvent-solute displacement. Experimental tests of the model indicate that each protein has a unique Z value and that Z is directly proportional to the molecular weight of a series of proteins when 60% formic acid is used as the mobile phase additive. This relationship is attributed to a direct relationship between Z and the contact surface area between polypeptide solutes and the support. Desorption curves for proteins also become more convex with increasingly molecular weight, as predicted by the retention model. In the solvent series of methanol, ethanol, propanol, the Z number decreases from the C1 to C3 alcohol. The Z number for any particular solvent is also related to other mobile phase additives, such as acids, and the concentration of additives.

High-performance hydrophobic interaction chromatography of proteins

A new, weakly hydrophobic, high-performance liquid chromatography column has been developed for the separation of native proteins based on their relative hydrophobicities. Starting with a covalently bound, hydrophilic polyamine matrix, packing materials were synthesized through acylation with anhydrides and acid chlorides of increasing chain length to obtain increasingly hydrophobic surfaces. Proteins in aqueous buffers were induced to bind hydrophobically to the columns by the use of high salt concentrations in the mobile phase. Elution was achieved by decreasing the ionic strength of the solvent in a linear gradient. A mixture of cytochrome c, conalbumin, and beta-glucosidase was used as a standard to test the resolving power of newly synthesized columns. On a 4-cm butyrate column, baseline resolution was achieved in 20 min with a gradient of 3.0 mu sodium sulfate in 0.1 M potassium phosphate buffer, pH 7.0, to water. The static loading capacity for each column was determined using a hemoglobin binding assay. Capacities normally ranged between 150 and 180 mg of hemoglobin per gram of support. Since proteins are not denatured in hydrophobic interaction chromatography, enzymes eluted from the column retained enzymatic activity. Samples of alpha-amylase and beta-glucosidase ranging in size from 10 to 200 micrograms were recovered from the butyrate column with greater than 92% enzymatic activity in all cases. In a single trial, the enzyme citrate synthase was recovered from the benzoate column with 92% retention of enzymatic activity.

High-performance liquid chromatography of biopolymers

The ability to separate biological macromolecules with good resolution on liquid chromatographic columns has depended on the development of suitable packing materials. In size exclusion chromatography, molecules are separated by size on the basis of differential permeation of the packing. Ion exchange, hydrophobic interaction (or reversed-phase), and affinity chromatography are all surface-mediated separation methods, although they depend on different retention mechanisms. High-performance liquid chromatographic columns designed for biopolymers offer major advantages over conventional columns in both speed and resolving power. The exponential growth of literature on the high-performance separation of peptides and proteins in particular indicates that the technique will become the dominant form of column liquid chromatography.

Mobile phase selection for the high-performance ion-exchange chromatography of proteins

Proper mobile phase selection significantly improved high-performance ion-exchange fractionations of proteins. The pH and salt content of the eluant affected chromatographic behavior on both strong and weak ion-exchange columns. The retention and resolution of a number of proteins was examined on strong and weak ion-exchange supports with regard to these mobile phase variables. The strong ion-exchange columns were found to be superior for the protein separations performed in this study. The selectivity of both weak and strong ion-exchange columns was pH dependent, however, strong ion-exchange columns were operable over a broader range of pH. Examination of the effect of salts demonstrated that their "displacing activity" could be divided into three categories: weak, intermediate, and strong with regard to the protein mixture utilized. Intermediate salts provided best resolution along with good recoveries. Strong displacing salts were useful for eluting strongly retained proteins. The selection of a mobile phase with respect to protein retention is discussed.

Separation of synthetic oligonucleotides on columns of microparticulate silica coated with crosslinked polyethylene imine

A rapid and effective method for separating oligonucleotides using high-performance ion-exchange chromatography is described. Columns were prepared by adsorbing a layer of polyethylene imine on 5-micron-diameter porous silica followed by crosslinking with a multifunctional oxirane. This weak anion-exchange matrix was found to be useful in the separation of mononucleotides and oligonucleosides containing up to 20 residues in either homo- or heteropolymers. Small analytical columns (4.2 X 150 mm) had a capacity ranging from less than a microgram in analytical separations to several milligrams in the preparative mode. The columns have proven to be especially useful in assessing the purity of precursor blocks, monitoring the chemical synthesis of oligonucleotides, and isolating reaction products after the synthesis.

A system for coupled multiple-column separation of proteins

Purification of proteins is commonly a multiple-step process involving size exclusion, ion exchange, affinity, hydrophobic, and other modes of chromatography. In an effort to circumvent the laborious process of collecting the solutes from each column and reintroducing them onto a second column, a valving system is described that directs the samples eluted from a high-performance liquid chromatographic column through a detector with a high-pressure cell into either a second column or into storage loops of a multiloop value. This multiloop value is referred to as a high-pressure fraction collector. After development of the first column is complete, a second solvent can be directed to the second column or high-pressure fraction collector to elute the solutes back through the detector and onto any other column in the system. The process of eluting a sample from a column through a single detector and directing it to the high-pressure fraction collector or any other column in the system may be repeated a number of times. Such valving systems make it possible to chromatograph a single protein component on two or three columns in a short time.

High-performance cation-exchange chromatography of proteins

Approximately one-third of all proteins reported in the literature have a pI sufficiently high to be resolved by cation-exchange chromatography. This paper reports the preparation and use of new high-performance polymeric-bonded-phase cation-exchange columns. Starting from a very stable, covalently bonded polyamide coating on microparticulate silica, simple derivatization produces a versatile cation-exchange material useful for separations traditionally performed on classical carboxymethylated soft gel supports. Column behavior was monitored using chymotrypsinogen, cytochrome c, and lysozyme as standards. The polymeric bonded phase was stable to pH 2.5 and exhibits enhanced selectivity for proteins due to a slight hydrophobic character of the matrix. Several separations of biological interest that demonstrate the utility of these small cation-exchange columns for modern biochemical separations are shown.

A reciprocating, single-needle hemodialyzer with bidirectional flow of sorbent suspension

Previous theoretical analysis has indicated that adequate mass transfer is possible in a dialyzer with reciprocating membrane motion provided that the dialysate concentration of uremic substances is kept low. Earlier models have utilized a collection of sorbents (charcoal, urease, and a cation exchanger) constrained next to the dialyzer membranes. We have designed a new dialyzer with a sorbent suspension having free access from a reservoir to the spaces between membrane packages. At a treatment rate of 150 ml/min/m2, the in vitro creatinine clearance is 75 ml/min/m2, which agrees within experimental accuracy with the theoretical prediction. The creatinine clearance, flow resistance, and compliance of the dialyzer are constant during four to six hours of testing. In vivo tests have been performed during urea and creatinine infusion in a normal dog and in a dog with 3/4 nephrectomy. The in vivo creatinine clearance agrees within 10% with the in vitro clearance. Sodium, potassium, calcium, and bicarbonate fluxes are acceptable for patients in renal failure. The new design allows a higher capacity for urea and creatinine, since larger amounts of sorbent may be used.

Reversed-phase supports for th resolution of large denatured protein fragments

Large pore (much greater than 300 A), spherical partical silica stationary phases possessing either C18 or C8 hydrocarbon ligands out-performed small pore (60-100A), irregular shaped silicas for the purification of large denatured peptides. Since columns 5 cm in length appeared to be as effective in separating peptides as columns 5 times longer, it is likely that large peptides absorb to the matrix rather than partition between the stationary and mobile phases.

Rapid analysis of bilirubin in neonatal serum. I. The binding of bilirubin to albumin

Evaulation of the severity of jaundice in the neonate may be determined by measuring the reserve binding capacity of serum proteins for free bilirubin. Determination of protein-bound bilirubin has been labor intensive, necessitating multiple runs on gel-permeation chromatography columns or, more recently, enzyme assays or fluorescence quenching analysis. We present a method for quantitation of free bilirubin and of bilirubin-binding capacity of serum by liquid chromatography. A gel-permeation column binds free bilirubin while allowing passage and quantitation of protein-bound bilirubin. Subsequent injection of a desorbing agent releases the adsorbed bilirubin from the column, permitting quantitation of free bilirubin. Bound and free serum bilirubin may be determined directly in less than 15 min using 10 microL of serum. The binding of bilirubin to neonatal serum is seen to be quite different from the binding to adult serum. Ion-exchange chromatography of adult and neonatal serum samples shows that their protein profiles are radically different. This difference probably accounts for the binding characteristics.

Rapid analysis of bilirubin in neonatal serum. I. The binding of bilirubin to albumin

Evaulation of the severity of jaundice in the neonate may be determined by measuring the reserve binding capacity of serum proteins for free bilirubin. Determination of protein-bound bilirubin has been labor intensive, necessitating multiple runs on gel-permeation chromatography columns or, more recently, enzyme assays or fluorescence quenching analysis. We present a method for quantitation of free bilirubin and of bilirubin-binding capacity of serum by liquid chromatography. A gel-permeation column binds free bilirubin while allowing passage and quantitation of protein-bound bilirubin. Subsequent injection of a desorbing agent releases the adsorbed bilirubin from the column, permitting quantitation of free bilirubin. Bound and free serum bilirubin may be determined directly in less than 15 min using 10 microL of serum. The binding of bilirubin to neonatal serum is seen to be quite different from the binding to adult serum. Ion-exchange chromatography of adult and neonatal serum samples shows that their protein profiles are radically different. This difference probably accounts for the binding characteristics.

Techniques for detecting enzymes in high-performance liquid chromatography

Techniques are described for the automated detection of a series of enzymes in a high-performance liquid chromatographic system. Detection was achieved by either a direct or a coupled enzyme assay using photometric detectors. In direct detection the immediate enzymatic product was monitored. Coupled enzyme assays required additional enzyme(s) to convert the product of the primary enzyme reaction into a more easily detectable form. The efficiency of both free and immobilized coupling enzyme(s) was evaluated. The detector sensitivity could be increased three-fold by increasing the reaction temperature. This system is particularly suitable for isoenzyme profiling in biological materials.

Rapid assessment of isoenzymes by high-performance liquid chromatography

We describe the rapid profiling of isoenzymes by use of microparticulate anion-exchange chromatography supports and a continuous, post-separation enzyme detector in a high-performance liquid chromatograph. Chromatographic analysis and enzyme detection are fully automated and provide excellent reproducibility. Factors affecting the isoenzyme profile and detector response characteristics are assessed. Lactate dehydrogenase and creatine kinase isoenzymes in tissue extracts, control materials used as electrophoretic standards, and serum were profiled by this method to establish the resolution and reliability of the method. We show the clinical use of this method in detecting changes in these isoenzymes in serum associated with acute myocardial infarction.

Rapid assessment of isoenzymes by high-performance liquid chromatography

We describe the rapid profiling of isoenzymes by use of microparticulate anion-exchange chromatography supports and a continuous, post-separation enzyme detector in a high-performance liquid chromatograph. Chromatographic analysis and enzyme detection are fully automated and provide excellent reproducibility. Factors affecting the isoenzyme profile and detector response characteristics are assessed. Lactate dehydrogenase and creatine kinase isoenzymes in tissue extracts, control materials used as electrophoretic standards, and serum were profiled by this method to establish the resolution and reliability of the method. We show the clinical use of this method in detecting changes in these isoenzymes in serum associated with acute myocardial infarction.

A continuous-flow enzyme detector for liquid chromatography

A detection system has been developed for the selective and sensitive detection of enzymes eluting from a liquid chromatographic column. This system monitors a reaction that the enzyme catalyzes and provides a chemical amplification ranging from 10(4) to 10(5). The detection system consists of a reagent or substrate pump, a post-column reactor packed with non-porous spherical glass beads, and a photometric detector. A linear and selective response to a series of enzymes of clinical importance is demonstrated.

Glycerolpropylsilane bonded phases in the steric exclusion chromatography of biological macromolecules

Glycerolpropylsilane bonded phases have been found to control the adsorption and/or denaturation of proteins and nucleic acids on controlled porosity glass supports. The bonded-phase thickness is 18-19A while the amount of glycerol moiety varies from 80 to 150 mumoles/g depending on support pore diameter. It has been demonstrated that carbohydrate bonded supports may be used in the chromatography of proteins, nucleic acids, and polysaccharides.

Identification of a ventral scent marking pheromone in the male Mongolian gerbil (Meriones unguiculatus)

Sebum from the ventral scent marking gland of the male Mongolian gerbil was fractionated and tested for its ability to elicit behavioral response in a conditioning task and in a stimulus preference situation. The active fraction was identified as phenylacetic acid; both it and a synthetic sample elicited the same behavioral response. Phenylacetic acid appears to be a major pheromone of the male Mongolian gerbil.

Chemical communication and "propaganda" in slave-maker ants

Slave-maker ants of the Formica sanguinea group direct their raids by means of odor trails. Artificial trails made from whole-body extracts and extracts of Dufour's glands and hindguts can be used to guide columns of workers to selected target colonies and to initiate raids. In workers of F. pergandei and F. subintegra, members of the F. sanguinea group, the Dufour's glands are hypertrophied and contain large quantities of three acetates (decyl, dodecyl, and tetradecyl), which are discharged at defending workers during the slave raids. The acetates produce very efficient, long-lasting alarm signals that attract the slave-makers but disperse the defenders; in effect, therefore, they are "propaganda substances."

Insect pheromones

The evidence for intraspecies chemical communication in insects is reviewed, with emphasis on those studies where known organic compounds have been implicated. These signal-carrying chemicals are known as pheromones. There are two distinct types of pheromones, releasers and primers. Releaser pheromones initiate immediate behavioral responses in insects upon reception, while primer pheromones cause physiological changes in an animal that ultimately result in a behavior response. Chemically identified releaser pheromones are of three basic types: those which cause sexual attraction, alarm behavior, and recruitment. Sex pheromones release the entire repertoire of sexual behavior. Thus a male insect may be attracted to and attempt to copulate with an inanimate object that has sex pheromone on it. It appears that most insects are rather sensitive and selective for the sex pheromone of their species. Insects show far less sensitivity and chemospecificity for alarm pheromones. Alarm selectivity is based more on volatility than on unique structural features. Recruiting pheromones are used primarily in marking trails to food sources. Terrestrial insects lay continuous odor trails, whereas bees and other airborne insects apply the substances at discrete intervals. It appears that a complex pheromone system is used by the queen bee in the control of worker behavior. One well-established component of this system is a fatty acid, 9-ketodecenoic acid, produced by the queen and distributed among the workers. This compound prevents the development of ovaries in the workers and inhibits their queen-rearing activities. In addition, the same compound is used by virgin queen bees as a sex attractant.