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Biomedical subjects

R Wetzel

Publications and source records attributed to R Wetzel.

104 records · Page 6Linked to original sources
PubMedDate not supplied

A general method for highly selective cross-linking of unprotected polypeptides via pH-controlled modification of N-terminal alpha-amino groups.

A method is described for the highly selective modification of the alpha-amino groups at the N-termini of unprotected peptides to form stable, modified peptide intermediates which can be covalently coupled to other molecules or to a solid support. Acylation with iodoacetic anhydride at pH 6.0 occurs with 90-98% selectivity for the alpha-amino group, depending on the N-terminal residue (as shown with a series of model hexapeptides containing a competing Lys residue). Although Cys residues must be protected (reversibly or irreversibly) before the anhydride reaction, there are no detectable side reactions of the alpha-amino moiety--of the reagent or of modified peptide--with the side chains of His, Met, or Lys. The reaction works well in denaturants, so that inhibitory effects of noncovalent structure can be minimized. In a second step the iodoacetyl-peptide can be reacted with a thiol group on a protein, on a solid chromatography matrix, on a spectroscopic probe, etc. This is illustrated by reaction of a series of N alpha-iodoacetyl-peptides with murine interferon-gamma, which contains a C-terminal Cys residue. Data are presented which suggest that this iodoacetic anhydride scheme is superior in selectivity for alpha-amino groups to conventional chemical approaches to cross-linking such as use of 2-iminothiolane or N-hydroxysuccinimide-activated carboxylic acid esters. The reaction is ideally suited for modifying peptide fragments, as pure species or as mixtures, derived from proteolytic or chemical fragmentation of proteins. Furthermore, polypeptides synthesized biosynthetically, for example via recombinant DNA techniques, can be cross-linked in this way.(ABSTRACT TRUNCATED AT 250 WORDS)

Acetic Anhydrides↗
PubMedDate not supplied

A novel method for the incorporation of glycoprotein-derived oligosaccharides into neoglycopeptides.

We describe a new method for the transfer of carbohydrate moieties to polypeptides in which complex carbohydrate, in the form of glycosyl amino acid, is removed from an available glycoprotein, derivatized, and reacted with a polypeptide via an iodoacetylated alpha-amino group. A family of oligomannose chains, N-linked to the side chain of Asn, was obtained from ovalbumin by pronase digestion and purified as previously described. A reactive sulfhydryl group was specifically placed on these molecules by reaction of 2-iminothiolane with the Asn alpha-amino group. Separately, the alpha-amino group of the peptide GGYR was specifically iodoacetylated by reaction with iodoacetic anhydride at pH 6. Reaction of the thiol-containing carbohydrate with iodoacetylated peptide at pH 8 gave in high yield the corresponding oligomannosyl-peptides, whose structures were confirmed by mass spectrometry. A peptide inhibitor of HIV protease was also oligomannosylated by this procedure. The principle advantage of this method is the efficiency of the reaction even when performed with stoichiometric amounts of the two molecules at low concentration. It should be feasible to extend this chemistry to larger polypeptides.

Acetylglucosamine↗
PubMedDate not supplied

[Sesamoid bone complex and hallux valgus deformity. A retrospective analysis of 82 Mitchell osteotomies].

The aim of the operative treatment of the hallux valgus deformity is to correct the medial luxation of the first metatarsal head out of the sesamoid complex, the restoration of a congruent joint, the patient after treatment should be painfree. 82 patients were available for an independent clinical and radiological review. The median follow up was 32 months. The evaluation of the results are based on objective and subjective assessment of the patients as well as on radiographic criteria, such as hallux valgus angle, intermetatarsal angle, shortening of the first metatarsal bone, subluxation, lateral positioning of the osteotomized MT I-head and position of the sesamoid complex. Depending on the degree of "lateralisation" of the sesamoid complex seven groups were defined: 0/0, 1/0, 1/1, 2/1, 2/2. 2/3, 3/3 following Appel. Following objective criteria 61% of the patients were evaluated excellent or good, following subjective criteria 77% were evaluated excellent or good. Isolated parallel shifting seems to be sufficient in mild forms of hallux valgus (sesamoid complex group 2/2 or less), while the severe subluxation in the metatarsophalangeal joint (sesamoid complex group 2/3, 3/3) requires an additional lateral wedge osteotomy.

Adolescent↗
PubMedDate not supplied

[Bone density--reference values in German men. A study of the lumbar spine with the Lunar-DPX-densitometer].

UNLABELLED: The DXA-technique is a well established method to study bone mineral density (BMD). Until now there are no reliable reference data based on the male population of Germany. QUESTION: Are the data base, given by the manufacturer transferable to the male population in Germany? METHODS: So a cross sectional study based on 715 healthy males with German ethnic background (age 20-89) was carried out. Comparison was made to the ap spine reference data of northern Europe. RESULTS: The peak bone mass was 1,26 +/- 0,17 g/cm2 at the age of 20-24 years. After that the BMD decreases to the sixth decade (1,09 +/- 0,18 g/cm2), further on there is an increase to 1,18 +/- 0,21 g/cm2 in the ninth decade. CONCLUSION: Looking at a comparable Swedish study there are no significant differences, looking at a Finnish study there are statistically significant differences in the sixth decade (t = 3,246) and seventh decade (t = 2,413). The results of our study complete the data base until now, but one should be careful to transfer the data base provided by the manufacturer.

Absorptiometry, Photon↗
PubMedDate not supplied

The role of cysteine oxidation in the thermal inactivation of T4 lysozyme.

Wild-type T4 lysozyme contains unpaired cysteine residues at positions 54 and 97. To investigate the role these residues play in the thermal inactivation of the wild-type, we constructed a double mutant with these cysteines replaced with valine and serine. This molecule, T4 lysozyme (C54V/C97S), is more stable than the wild-type to inactivation at 70 degrees C at pH 6.5 and 8.0. Guanidine hydrochloride reactivation experiments and SDS-PAGE on the inactivated products show that the wild-type is susceptible to varying degrees of oxidative damage, depending on buffer conditions, while the cysteine-minus mutant inactivates only by other pathways. The products of thermal, oxidative inactivation of the wild-type are disulfide-linked oligomers. The dependence of inactivation rate on temperature suggests that the formation of these aggregates depends on prior thermal unfolding of the T4 lysozyme molecule.

Amino Acid Sequence↗
PubMedDate not supplied

[Active stabilization of the acetabular floor by auto-/homologous bone transplantation in inflammatory rheumatic protrusion hip].

Inflammatory changes of the hip joint in rheumatoid arthritis often lead to secundary protrusio acetabuli. Total joint replacement may lead to problems, especially in mounting the acetabular component firmly to the pelvis. For about 7 years we have been using the so-called "active stabilisation of the acetabular floor" by implantation of autologeous bone prepared from the resected femoral neck. In changing the artificial joint homologeous bone from our bone bank was used. Up to Dec. 31, 1983 neither graft versus host reactions nor failure in healing were seen. 107 total joint replacements with bone transplantation in rheumatoid arthritis were performed. In all cases we could see optimal growing in of the transplanted bone, often confirmed by X-ray tomograms, with good support of the acetabular component. So far we have not seen any negative results. The active stabilisation of the acetabular floor seems to be a worthwhile addition to known surgical possibilities.

Acetabulum↗