Synthesis and protein-binding properties of spacer-free thioalkyl agaroses

Interaction of fibrinogen with n-alkylagaroses and its purification by critical hydrophobicity hydrophobic interaction chromatograpy

A rational application of hydrophobic interaction chromatography (HIC) to the purification of proteins has remained an enigma in spite of over 30 years of research. The critical hydrophobicity parameter, which can be determined from a concentration series of n-alkyl Sepharose 4B (Seph-Cn) offers the possibility of adapting the HIC gel to the needs of purification. To this end a library of HIC gels (Seph-C4 to Seph-C6) of different immobilized alkyl residue concentrations was synthesized and tested with purified bovine fibrinogen. Binding of fibrinogen to such a concentration series resulted in sigmoidal binding curves. Analysis of the Seph-C5 data according to the lattices-site binding model yielded adsorption coefficients (nS) between 5 and 10 indicating that 5-10 lattice-sites (alkyl residues) interact multivalently with a fibrinogen molecule for adsorption at low ionic strength. The apparent lattice-site half-saturation constant of dissociation lies between 21 and 25 micromol/ml packed gel. For each alkyl chain length a critical hydrophobicity could be determined. For fibrinogen purification the critical hydrohobicity gel, Seph-C5 (13 micromol/ml packed gel), was selected. With the help of the cosolvents NaCl or glycine a fully reversible adsorption of fibrinogen could be facilitated on the critical hydrophobicity gel. Application of the method to human and bovine blood plasma resulted in a single step purification of fibrinogen in high yields. A comparison of the classical purification of fibrinogen with the critical hydrophobicity HIC (CHIC) method demonstrates a reduction in preparation time from several days to ca. 1 h. The subunit structure of HIC-purified human fibrinogen is identical to the classically purified protein. In the case of bovine fibrinogen however HIC-purified fibrinogen displayed a different subunit structure in that the Aalpha chain of fibrinogen had a ca. 5 kDa higher molecular mass. This may be due to the rapidity of the new one-step method and an avoidance of proteolysis.

Dendrimer-activated surfaces for high density and high activity protein chip applications

Highly functional Si and glass surfaces for protein immobilization have been prepared by a facile activation of native surface silanol groups. Poly(propyleneimine) dendrimers of generations 1-5 were immobilized onto the surface using a facile room-temperature coupling procedure that involved activation of native silanol groups of glass using 1,1'-carbonyldiimidazole under anhydrous conditions. The dendrimer-coated surfaces were used to immobilize proteins and were characterized with respect to surface loading and activity. A number of different chemical, physical, and biochemical techniques including contact angle measurement, ellipsometry, and fluorescence microscopy were used to characterize the resulting surfaces. Increasing the dendrimer generation past G-3 led to increased surface amine content, immobilized protein concentration, and the activity of immobilized alkaline phosphatase (used as a test system). Very high activity of the immobilized proteins in the case of higher generation (G-4 and G-5) dendrimers led us to conclude that such an approach has true potential for creating highly functional surfaces for protein chip applications.

Salt-independent adsorption chromatography: new broad-spectrum affinity methods for protein capture

The role of chromatography in capture is reviewed in terms of the special requirements imposed by the processing of very crude feedstocks. Adsorption methods which are not significantly affected by variations of feedstock ionic strength are highlighted. Methods are compared in terms of simplicity, robustness, selectivity and ease of elution. The application of such methods to enzyme and antibody purifications is summarised. Particular emphasis is placed on high ligand density methods, which have potential for broad-spectrum application.

Protein adsorption on low temperature isotropic carbon: V. How is it related to its blood compatibility?

Based on our research on blood protein interactions with low temperature isotropic carbon (LTIC) and data from the literature, we propose that the carbon surface has strong interactions with adsorbed proteins. In this paper we focus on how a relatively blood-compatible material interacts with plasma proteins. We present our results on the structure and properties of the LTIC surface utilizing SEM, STM, XPS, and contact angle measurements. We briefly review protein adsorption on LTIC using DSC, impedance, radioisotopes, and two-dimensional gel electrophoresis. LTIC is characterized by a microporous, oxidized, hydrophobic, and domain mosaic structure. Surface polishing smoothens the roughness and removes the porosity, while largely destroying the ordered atomic texture, making the surface more random and more amorphous. The LTIC surface denatures all adsorbed proteins studied. The rate of protein adsorption is high and the surface concentration is large. The LTIC surface adsorbs all proteins without preference. The surface also tenaciously retains proteins such that they cannot be displaced by buffer or exchanged by proteins in solution. We conclude that LTIC accomplishes its blood compatibility through a passivating film of strongly adsorbed bland proteins, which do not interact with platelets nor participate in blood coagulation. We also suggest mechanisms for the production of such a film by the LTIC surface.

Analysis of affinity supports by 13C CP/MAS NMR spectroscopy: application to carbonyldiimidazole- and novel tresyl chloride-synthesized agarose and silica gels

A major problem in affinity technology is the analysis of the synthesized solid supports, since liquid phase methodology can generally not be applied. Recently we reported a novel reaction sequence for the 2,2,2-trifluoroethanesulfonyl chloride (tresyl chloride) coupling of nucleophiles [Demiroglou et al. (1994) Angew. Chem. Int. Ed. Engl. 33, 120-123] to agarose and concluded that previously proposed structures could not be correct. However it was not possible for us to conclusively define the new reaction products because the agarose derivatives could not be solubilized for customary liquid state 13C NMR analysis. Therefore in this paper solid state 13C CP/MAS NMR spectroscopy is applied for the first time to the polysacharide agarose. Using alkyl agarose derivatives prepared by the carbonyldiimidazol method as control we found that reliable spectra in agreement with the published reaction mechanism could be obtained. The method was then applied to the novel reaction products of the tresyl chloride reaction. From the solid state 13C NMR spectra and other quantitative data it is concluded that a beta-sulfonyl carboxylic acid is generated during alkaline hydrolysis of tresyl agarose and that alkyl amines are coupled by a beta-sulfonyl amide bond in an elimination-addition reaction in the absence of SO- and SC-scission of the tresyl group. In the case of alkane thiol coupling the absence of SC-scission cannot be demonstrated indicating either a different reaction mechanism or possibly a mixture of reaction products.

Cyanogen bromide and tresyl chloride chemistry revisited: the special reactivity of agarose as a chromatographic and biomaterial support for immobilizing novel chemical groups

The cyanogen bromide and tresyl chloride (2,2,2-trifluoroethanesulfonyl chloride) methods belong to the best-known activation procedures for solid supports in biochemistry. In both cases the originally proposed reaction mechanisms were revised many years later. In this paper important aspects of these two major activation reactions in connection with the singular polysaccharide support, agarose, will be treated with emphasis on the novel reaction mechanism recently proposed for tresyl chloride. In addition, the special role played by sulfur in the new uncharged alkyl-S-S-gels is examined in connection with the phenomenon of base-atom recognition.

Base-atom recognition in protein adsorption to alkyl agaroses

The three proteins phosphorylase b, calmodulin and fibrinogen are adsorbed onto thioalkyl derivatives of Sepharose much more strongly than onto gels carrying the same alkyl residue coupled via a carbamate linkage. This enhancement of binding onto alkyl-S-Sepharoses compared with alkyl-N-agaroses is not primarily due to an increase in the extent of conformational changes of the proteins occurring on the gel surface. This can be shown in experiments with the tripeptide Trp-Trp-Trp. The Trp tripeptide is also adsorbed with a much higher affinity to butyl-S-Sepharose than to butyl-N-Sepharose, showing that the primary interaction between the immobilized alkyl residue and the amino acids of the protein is decisive for adsorption. A model stressing the strong influence of an atom or a group of atoms at the base of an immobilized alkyl residue is described as "base-atom recognition".

Ca(2+)-dependent ubiquitination of calmodulin in yeast

Recently we were able to show that calmodulin from vertebrates, plants (spinach) and the mold Neurospora crassa can be covalently conjugated to ubiquitin in a Ca(2+)-dependent manner by ubiquityl-calmodulin synthetase (uCaM-synthetase) from mammalian sources [R. Ziegenhagen and H.P. Jennissen (1990) FEBS Lett. 273, 253-256]. It was therefore of high interest to investigate whether this covalent modification of calmodulin also occurs in one of the simplest eukaryotes, the unicellular Saccharomyces cerevisiae. Yeast calmodulin was therefore purified from bakers yeast. In contrast to calmodulin from spinach and N. crassa it does not activate phosphorylase kinase. Crude yeast uCaM-synthetase conjugated ubiquitin Ca(2+)-dependently to yeast and mammalian (bovine) calmodulin. Yeast calmodulin was also a substrate for mammalian (reticulocyte) uCaM-synthetase. As estimated from autoradiograms the monoubiquitination product (first-order conjugate) of yeast calmodulin has an apparent molecular mass of ca. 23-26 kDa and the second-order conjugate an apparent molecular mass of ca. 28-32 kDa. Two to three ubiquitin molecules can be incorporated per yeast calmodulin. Experiments with methylated ubiquitin in the heterologous reticulocyte system indicate that, as with vertebrate calmodulins, only one lysine residue of yeast calmodulin reacts with ubiquitin so that the incorporation of multiple ubiquitin molecules will lead to a polyubiquitin chain. These results also indicate that the ability of coupling ubiquitin to calmodulin was acquired at a very early stage in evolution.