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Biomedical subjects

J Porath

Publications and source records attributed to J Porath.

At least 73 records · Page 4Linked to original sources
PubMed1983

Immobilized-metal affinity chromatography of serum proteins on gel-immobilized group III A metal ions.

A chromatographic adsorbent (TED-Sepharose) capable of chelating various di- and trivalent metal ions was prepared by introducing tris(carboxymethyl)ethylenediamine into agarose. This gel was charged with Al3+, Ga3+, In3+, and Tl3+ to form immobilized-metal affinity adsorbents, and their adsorption behavior toward serum proteins at various pH values was studied. At low pH, these adsorbents behave as ion exchangers. At pH 7 and above, their adsorption behavior shows a high degree of selectivity but with varying affinity profiles for serum proteins. The adsorbents based on Al3+ and Ga3+ thus have negligible affinity for proteins at pH 7.6, whereas that based on In3+ exhibits a low but significantly higher affinity for proteins compared to the previous two. On the other hand, the Tl3+-based adsorbent showed a much higher capacity to adsorb serum proteins. Selective fractionation by affinity elution of human serum proteins adsorbed to an immobilized Tl3+ is also presented.

Blood Proteins↗
PubMed1980

Metal chelate affinity chromatography. I. Influence of various parameters on the retention of nucleotides and related compounds.

The influence of various parameters, such as pH, ionic strength and temperature, on the retention of different nucleotides and related compounds on copper chelate gels has been investigated in order to understand the respective roles played by the different solute constituents (i.e., heterocyclic bases, sugars and phosphate groups) in the interaction and to define optimal conditions for subsequent application to the fractionation of oligo- and polynucleotides.

Biopolymers↗
PubMed1979

Charge-transfer and water-mediated adsorption. III. Adsorption on tryptophan-substituted Sephadex and Sepharose.

The adsorption of tyrosine, tryptophan and some related compounds on tryptophan and tryptophanyltryptophan gels is similar to but much stronger than that observed with the parent gel Sephadex G-25. The adsorption has been attributed mainly to charge transfer or redistribution of electrons and protons leading to pi-bonding and hydrogen bonding, in addition to hydrophobic adsorption. The participation of organized water surrounding the gel matrix, the ligands and the solute molecules has been considered. The application of this principle of adsorption has been exemplified by chromatographic experiments with a cellulase preparation of tryptophan-Sepharose 4B.

Amino Acids↗
PubMed1979

Neurite outgrowth elicited by embryonic chick heart: partial purification of the active factor.

Chick heart explants stimulate a dense outgrowth of neurites in co-cultured spinal, sympathetic and ciliary ganglia. A factor sharing these properties was partially purified by gel filtration of extract prepared from lyophilized 18-day embryonic hearts. The active factor has an apparent molecular weight of roughly 40,000 and is evidently distinct from nerve growth factor (NGF) by stimulating the parasympathetic ciliary neurons and by lack of cross-reactivity with antibodies to NGF.

Animals↗
PubMed1976

Immobilization of enzymes based on hydrophobic interaction. I. Preparation and properties of a beta-amylase adsorbate.

Sweet potato beta-amylase (alpha-1,4 glucan maltohydrolase, EC 3.2.1.2) was immobilized through adsorption onto an agrose gel to which nonpolar side chains had been introduced via ether bridges. The adsorbent showed evidence of saturation at an enzyme content of 35 mg per milliliter of packed gel. The adsorption was rapid and yielded a product whose operational stability depended on the initial content of beta-amylase. Activity leakage was low. The relative activity of immobilized enzyme was inversely related to the amount of enzyme adsorbed to a given gel volume, having a maximal value of around 50% at low enzyme contents.

Adsorption↗
PubMed1976

Immobilization of enzymes based on hydrophobic interaction. II. Preparation and properties of an amyloglucosidase adsorbate.

Amyloglucosidase from Aspergillus niger (alpha-1,4 and 1,6 glucan glucohydrolase, EC 3.2.1.3) was immobilized through adsorption onto a hexyl-Sepharose, containing 0.51 mol hexyl-group per mole of galactose. The adsporption limit of the carrier with respect to this enzyme was about 17 mg per gram wet conjugate. The retention of activity upon immobilization was high, varying from essentially full activity at low enzyme content down to 68% at the adsorption limit. The immobilized preparation, as well as the soluble enzyme, showed apparent zero order kinetics within 60% of the substrate's conversion limit. Product inhibition of the soluble enzyme showed a KI of 5-10(-2)M. In the presence of 3M NaCl, adsorbates were formed more rapidly and with a higher yield of immobilized protein, but with lower specific activity. Conjugates resulting from adsorption of amyloglucosidase in identical concentrations, but at different salt contents, showed comparable activities and operational stabilities. Continuous operation from three months reduced conjugate activity to 40%. The thermal stability of the adsorbate was inferior to that of the soluble enzyme, but was noticeably enhanced in the presence of substrate.

Adsorption↗
PubMed1976

Immobilization of enzymes based on hydrophobic interaction. III. Adsorbent substituent density and its impact on the immobilization of beta-amylase.

Hexyl-groups have been introduced into crosslinked Sepharose 6B, yielding gels with degrees of substitution which range from 0.02 to 0.70 mol hexyl-side chain per mole galactose residue. The gels were exposed to beta-amylase in solution, and the resulting adsorbates indicated a monotonic increase in adsorption capacity with an increasing hexyl-content. Adsorbate activity, by contrast, displayed a maximum for a carrier gel with a hexyl-galactose ratio of 0.51. Adsorbates based on gels with different hexyl-content were used in column reactors for continuous maltose production from a soluble starch substrate.

Adsorption↗
PubMed1975

The trypsin and chymotrypsin inhibitors in chick peas (Cicer arietinum L.). Purification and properties of the inhibitors.

From a crude extract of chick peas (Cicer arietinum L.) inhibitors of trypsin and chymotrypsin were isolated by affinity chromatography on a column of trypsin-Sepharose 6B. The content of inhibitors was found to be 1.5 g/kg. They were further separated into six isoinhibitors by ion-exchange chromatography on DEAE-Sephadex A-25. Two of the isoinhibitors accounted for about 50% of the isolated inhibitors and were further purified to a homogeneous state. The isoinhibitors had a molecular weight of about 10000 as determined by molecular-sieve chromatography on Sephadex G-75. They were stable towards extremes of pH and temperatures up to 75 degrees C or towards digestion by pepsin. They were also stable in 6 M urea but not in 6 M guanidine-HCl. The intact inhibitors were destroyed when the peas were cooked at 100 degrees C or when they were toasted at 130 degrees C. The four major inhibitors had similar amino acid compositions and did not contain detectable amounts of free sulfhydryl groups, tryptophan or carbohydrate. Cysteine is the dominant amino acid residue in all of them and accounted for about 20% of their amino acid content. The isoelectric point of the isoinhibitors lies in the range of pH 4.9-8.6 and two of the major inhibitors had isoelectric points of pH 4.75 and pH 4.96. They inhibited chymotrypsin to the same extent but differed in their inhibitory activities towards trypsin, indicating that they are mixtures of native and trypsinmodified forms and that they probably have separate sites for the two enzymes. They did not inhibit other proteolytic enzymes belonging to two groups (i.e., serine or cysteine enzymes) or originating from different sources (i.e., animals, plants or bacteria).

Amino Acids↗