PubMed Health⌕ Search

Biomedical subjects

A Undén

Publications and source records attributed to A Undén.

At least 19 recordsLinked to original sources
PubMed2000

Study of the alkylation propensity of cations generated by acidolytic cleavage of protecting groups in Boc chemistry.

The alkylation of cysteine residue by different classes of carbonium ions, derived from the cleavage of side chain protective groups in anhydrous HF, was investigated. It was found that side chain protection as beta-2,4-dimethylpent-3-yl ester (Dmp) or 2,4-dimethylpent-3-yloxycarbonyl (Doc) groups resulted in more than seven-fold lower level of alkylated byproducts. This makes Dmp and Doc protection of amino acid side chain during solid phase synthesis particularly valuable in the synthesis of peptides containing cysteine residues or other functional groups prone to alkylation by carbonium ions.

Alkylation↗
PubMed1997

A quantitative structure-activity relationship study of some substance P-related peptides. A multivariate approach using PLS and variable selection.

Nine new analogues of substance P (SP) were designed using quantitative sequence-activity models based on the amino acid z-scales with PLS as the statistical method and the GOLPE procedure for variable selection. The nine SP analogues were synthesised by solid-phase peptide synthesis and tested for affinity to the NK-1 receptor from rat brain with radio receptor assay using [125I]-Bolton-Hunter substance P as labelled ligand. All of the new substance P analogues showed high affinities, with IC50 values of less than 0.8 nM. One analog, Lys-Arg-Ala-Lys-Phe-Met-Met-Phe-Phe-Gly-Leu-Let-NH2, showed a exceptional high affinity for the NK1 receptor, with IC50 = 5 pM.

Animals↗
PubMed1996

Backbone-to-backbone cyclized and linear pseudopeptide analogs of substance P as ligands to the substance P receptor from rat brain.

Two series of backbone modified substance P analogs were synthesized. In the first group of analogs the N-terminal region of substance P, SP(1-4), was replaced by a polyamine segment or aliphatic omega-amino fatty acid residues. Two of these analogs displaced 125I-Bolton-Hunter labeled substance P from rat brain synaptosomes with IC50 values of 1.3 +/- 0.5 and 1.6 +/- 0.3 nM, respectively. These affinities are similar to that of substance P (IC50 1.3 nM). The second group of analogs were a set of backbone-to-backbone cyclized pseudopeptides. In these analogs two peptide bonds at the C-terminal portion of substance P were replaced by the reduced peptide bonds (psi[CH2NH]) which were further reductively alkylated with 3(4-methylbenzylthio)propanal. After cleavage from the resin the peptides were oxidized into a cyclic disulfide. All of the cyclic analogs of substance P interacted with the NK1 receptor from rat brain with IC50 values in the micromolar range.

Animals↗
PubMed1996

Quality of life in octogenarians after valve replacement due to aortic stenosis. A prospective comparison with younger patients.

BACKGROUND: Results of aortic valve surgery in octogenarians have been evaluated as event-free survival. However, little attention has been given to quality of life aspects. METHODS: Thirty-two consecutive patients, mean age 83 +/- 2 years, undergoing valve replacement due to aortic stenosis, were compared to 30 patients, mean age 71 +/- 3 years, undergoing the same procedure. Mortality, morbidity and quality of life were studied. An interview was performed before surgery and 3 and 12 months postoperatively. The questionnaire contained items related to self-rated health, symptoms, physical ability, sleep disturbances and social and emotional functioning. RESULTS: Pre-operatively the older patient group was in a worse condition with a higher NYHA functional class and a more pronounced cardiomegaly. They had more cardiac symptoms and were more depressed. The control group had a higher score for physical ability and rated their quality of life as better. Postoperatively there was a higher early mortality rate in the octogenarians (9% vs 0%; ns). After 3 months, improvement of functional status and relief of symptoms was observed in both groups. Physical ability improved and the depression score decreased significantly in both groups. Self-rated health and quality of life improved. One year after valve replacement the improvement in quality of life was of a similar magnitude in the two groups. CONCLUSION: Following aortic valve replacement, octogenarians, despite a more compromised pre-operative status showed an improvement in symptomatology, physical ability and general well being, of a similar magnitude to that of the younger patients group. These findings lend further support to the recommendation that valve replacement should be performed in octogenarians with symptomatic aortic stenosis.

Aged↗
PubMed1996

Design of protecting groups for the beta-carboxylic group of aspartic acid that minimize base-catalyzed aspartimide formation.

With the objectives of developing new protecting groups for the beta-carboxyl group of aspartic acid that are resistant to base-catalyzed aspartimide formation and of evaluating the importance of sterical factors in the design of such protecting groups, four new alkyl ester derivatives of aspartic acid were synthesized. The beta-3-pentyl, beta-4-heptyl, beta-2,6-dimethyl-4-heptyl and the recently described beta-2,4-dimethyl-3-pentyl esters of Boc-aspartic acid were incorporated into model peptides, and the resin-bound protected peptides were treated with 20% piperidine for 10 h. The levels of aspartimide-related side products were compared with the previously reported beta-cyclohexyl, beta-menthyl and beta-2-adamantyl esters of aspartic acid. The results show that bulky, acyclic, aliphatic protecting groups (in particular the 2,4-dimethyl-3-pentyl ester) are significantly more resistant to base-catalyzed aspartimide formation than comparably rigid cyclic alkyl esters that under the same reaction conditions form several-fold more aspartimide-related side products. Using elevated temperatures to overcome difficult couplings leads to the formation of significant amounts of aspartimide when aspartic acid is protected with the cyclohexyl group, but the 2,4-dimethyl-3-pentyl protecting group offers excellent protection under these conditions. The use of the 2,4-dimethyl-3-pentyl protecting group will allow the use of orthogonally removable base-labile protecting groups in Boc chemistry and suggests a design of protecting groups for other nucleophile-sensitive trifunctional amino acids in both Boc and Fmoc chemistry.

Aspartic Acid↗
PubMed1995

Peptides as active probes.

The use of peptides as probes of peptide binding sites of neuropeptide receptors, and of peptidases and proteases is discussed. The rapidly expanding use of peptide antigens as probes of protein structure and valuable diagnostics and vaccines is described. We also discuss the use of synthetic peptide motifs in studies on the molecular details of protein-protein and protein-nucleic acid interactions. Covalently modified peptides such as phosphopeptides exemplifies the use of synthetic peptides in the study of posttranslational modifications of proteins.

Amino Acid Sequence↗
PubMed1994

A new class of compounds, peptide derivatives of adenosine 5'-carboxylic acid, includes inhibitors of ATP receptor-mediated responses.

A new type of ligand for the study of P2-purinergic receptor subtypes was synthesized by combining and modifying conventional nucleoside chemistry with Fmoc solid phase peptide synthesis techniques. The tri- and tetra-aspartic acid derivatives of adenosine-5'-carboxylic acid (AdoCAsp3 and AdoCAsp4) were found to act as weak agonists at P2-purinergic receptors, (activated by ATP and UTP respectively) present on C6 glioma cells. AdoCAsp4 induced inositol 1,4,5-trisphosphate formation in the C6 cells with an EC50 of 73 microM. In addition, AdoCAsp4 was found to inhibit (IC50 approximately 80 microM) ATP-induced cytosolic [Ca2+] transients in these glioma cells. The glycine derivative, AdoCGly, increased evoked release of noradrenaline from mouse vas deferens slices, probably due to the blockade of presynaptic P2-autoreceptors. The possibility that aspartic, glutamic or gamma-carboxyglutamic residues may be used to replace phosphate groups on an ATP receptor ligand, opens up new ways in ligand design.

Adenosine↗
PubMed1994

A new general solid-phase method for the synthesis of backbone-to-backbone cyclized peptides.

A model peptide with the sequences Ala-Pro-Lys(2ClZ)-Tyr(2BrZ) was synthesized on a 4-methylbenzhydryl amine (MBHA) polystyrene resin using conventional Boc/benzyl protective group strategy. The amino acid aldehyde Boc-valinal was coupled by reductive alkylation with NaCNBH3 in acidified DMF for 1 h. The secondary amine in the peptide-resin Boc-Val psi[CH2NH]Ala-Pro-Lys(2ClZ)-Tyr(2BrZ)-MBHA was reductively alkylated by 3(4-methylbenzylthio)-propanal at 40 degrees C for 6 h, resulting the peptide-resin Boc-Val psi[CH2N(CH2CH2CH2-S-pMeBzl)]Ala-Pro-Lys(2ClZ)-T yr(2BrZ)-MBHA. After the removal of the Boc group the synthesis was continued employing the above-mentioned methods, which led to the resin-bound peptide Leu psi[CH2N(CH2CH2CH2S-pMeBzl)]Ser-Pro-Gly-Lys(2ClZ )-Val psi [CH2N(CH2CH2CH2-S-pMeBzl)]Ala-Pro-Lys(2ClZ)-Tyr( 2BrZ)-MBHA. The peptide was cleaved from the resin with hydrogen fluoride. Reversed-phase HPLC and plasma desorbtion mass spectrometry analysis showed that the expected peptide Leu psi[CH2N(CH2CH2CH2SH)]Ser-Pro-Gly-Lys-Val psi[CH2N(CH2CH2CH2-SH)] Ala-Pro-Lys-Tyr-NH2 was obtained as the major product with low levels of side products. Intramolecular oxidation of the thiols gave the backbone to backbone cyclized peptide Leu psi[CH2N(CH2CH2CH2S)]Ser-Pro-Gly-Lys- Val psi[CH2N(CH2CH2CH2-S)]Ala-Pro-Lys-Tyr-NH2.

Alkylation↗
PubMed1994

Analogs of galanin (1-16) modified in positions 1-3 as ligands to rat hypothalamic galanin receptors.

Structure-activity relationship (SAR) studies have revealed that the first three residues of galanin (Gly1-Trp2-Thr3) are of critical importance for high-affinity binding to the galanin receptor. Furthermore degradation studies have shown that galanin is easily cleaved to yield inactive fragments in rat hypothalamus (t1/2 = 100 min). To obtain galanin receptor ligands with long-lasting biological activity the amino-terminus of galanin must be protected. We have therefore synthesized analogs of rat galanin(1-16) carrying modifications at the three amino-termini of galanin. All modifications of the peptide backbone flanking Trp2 as in the analogs [N-Me-Trp2]-galanin(1-16), [Tcc2]-galanin-(1-16), (Trp2-psi[CH2NH]-Thr3)-galanin-(1-16) produced a dramatic loss of affinity toward the galanin receptor. [N-Me-Thr3]-galanin(1-16) was the most active of the peptide backbone modified analogs (KD = 997 +/- 1 nM). Modifications of the indole ring in Trp2 ([For-Trp2]-galanin-(1-16), [Tcc2]-galanin-(1-16)) yielded analogs which, at concentrations up to 10 microM, did not displace [125I]galanin binding. N-Methylation of Gly1 by the introduction of sarcosine ([Sar1]-galanin(1-16)) did not significantly affect the ligand-binding properties of galanin(1-16) (KD = 8.7 +/- 0.1 nM).

Amino Acid Sequence↗
PubMed1993

New method for the synthesis of N-methyl amino acids containing peptides by reductive methylation of amino groups on the solid phase.

Primary amino groups on the model peptide Xaa-Ala-Pro-Lys(ClZ)-Tyr(2BrZ), synthesized on a p-methylbenzhydryl amine resin with conventional Boc/benzyl protective group strategy, were reacted with 4,4'-dimethoxydityl chloride in dichloromethane, resulting in the introduction of the dimethoxydityl group, which is an acid-labile N-alkyl type of protective group. The secondary amino groups thereby formed can be methylated by treating the peptide-resin with formaldehyde and sodium cyanoborohydride in N,N-dimethylformamide. After the removal of the dimethoxydityl group with trifluoroacetic acid, the resulting N-methylated amino acid residues with a free secondary amino groups are accessible for acylation with the next activated Boc amino acid. With this method majority of the 20 common amino acids can be monomethylated directly on the resin and, in most cases, with very low levels of the side reactions. In the cases where the complete methylation is difficult to achieve, the remaining primary amino groups can be selectively acylated in the presence of secondary amino groups with trimethylacetic acid 1-hydroxybenzotriazole ester. The method provides a convenient general route to synthesize N-methylated derivatives of most of the occurring and synthetic amino acids.

Amino Acid Sequence↗
PubMed1992

Orthogonal solid-phase synthesis of a monobiotinylated analog of neuropeptide Y.

Analogs of Neuropeptide Y (NPY) were synthesized with conventional Boc/benzyl protective group strategy. Instead of Asn7 in the native sequence, Boc-Lys(Alloc)-OH was incorporated. At the end of the synthesis the Alloc group was selectively removed by palladium-catalyzed hydrostannolysis and biotin coupled to the epsilon-amino group of Lys7. After cleavage and characterization with plasma desorption mass spectrometry the N epsilon,7-biotinyl-[Lys7]-NPY and the nonbiotinylated analog [Lys7]-NPY were investigated as ligands to the NPY receptor from rat cerebral cortex. Both analogs were found to be high affinity ligands to the NPY receptor and bound with essentially the same affinity as unmodified NPY.

Animals↗
PubMed1991

Investigation of the importance of the N-terminal peptide bonds of substance P by synthetic pseudopeptide analogs.

Synthetic Substance P analogs where each of the first five peptide bonds are replaced by the peptide bond surrogate Gly psi [CH2CH2]Gly are investigated as ligands to the Neurokinin 1 (NK1) receptor from rat cerebral cortex. The affinities of these analogs are then compared with the corresponding Gly-Gly analogs. With this model system replacement of the peptide bond between position 4 and 5 with psi [CH2CH2] resulted in a 7-fold reduction of affinity. Substitution of other peptide bonds resulted in only minor changes in affinity. Although the N-terminal hexapeptide is important for high affinity binding to the NK1 receptor the present study provides evidence for that this effects is not caused by the side chains of the amino acids in position 1-6 or as results of intramolecular hydrogen bonding with the C-terminal part of the peptide. A possible exception is the peptide bond that in the native peptide connects Pro4 and Gln5.

Animals↗
PubMed1991

Linear and cyclic N-terminal galanin fragments and analogs as ligands at the hypothalamic galanin receptor.

The neuropeptide galanin (1-29) binds with high affinity to hypothalamic receptors (KD approximately 0.9 nM) and regulates feeding behavior. The N-terminal fragments (1-16), (1-16)NH2 are high affinity (KD approximately 6 nM) full agonists in vivo and in vitro. L-Ala substitutions show that amino acid residues Gly1, Trp2, Asn5, Tyr9, and Gly12 are important for the high affinity binding of galanin (1-16). Shortening the fragment (1-16) to galanin (1-7) causes a gradual drop of affinity: galanin (1-15), (1-14), and (1-13) have submicromolar KD values and galanin (1-12) has KD approximately 3 microM. Cyclic analogs of galanin (1-12) of different ring size were synthesized by condensing Gly1 and Gly12 without or with spacer groups. These analogs, independent of ring size, had a lower affinity than the linear galanin (1-12). Derivatization of the N-terminus of galanin (1-29), (1-16), and (1-12) all resulted in a large drop of affinity for the receptors, suggesting again the importance of the free N-terminal Gly.

Alanine↗
PubMed1991

Protective immunogenicity of synthetic peptides selected from the amino acid sequence of Bordetella pertussis toxin subunit S1.

Five synthetic peptides identified as antigenic sites on the S1 subunit of pertussis toxin (PT) were coupled to the diphtheria toxin cross-reactive mutant protein CRM 197 or BSA. All peptide conjugates were immunogenic in animals. Two peptide-CRM-conjugates, corresponding to amino acids 1-17 and 169-186, induced especially high antibody titers against native PT in mice (Balb/c, C57/Black and outbred NMRI) as measured by ELISA. Upon in vivo PT challenge (0.5 microgram toxin) of the NMRI mice both the CRM and BSA conjugates of these two peptides fully protected the mice from PT induced leucocytosis. Some of the protected mice receiving peptide 1-17 conjugate had very low antibody titers against PT but high titers against the peptide as measured by ELISA, showing that PT-ELISA does not always reflect in vivo protection. A booster response against PT was noted upon challenge with PT in mice receiving peptide 1-17 or peptide 169-186 conjugate. Antibodies against peptide 170-186 could not be evaluated by ELISA since conjugates of this peptide (like PT itself) bind to immunoglobulins. They may also caused clustering of CHO cells. Rabbit antiserum to the peptide 1-17-CRM conjugate was highly efficient in inhibiting the ADP-ribosylating activity of PT with bovine transducin as substrate whereas the rabbit antiserum raised against the peptide 169-186-CRM conjugate neutralized the clustering effect of PT on CHO cells. Thus there is no concise correlation between the in vivo protection against PT challenge and the in vitro methods used for measuring antibody levels against PT (neutralization of the enzyme activity, the CHO cell clustering activity and titers in PT-ELISA). The CRM-conjugates of these two peptides constitute the first synthetic pertussis vaccine candidate with the ability to provide a chemically well defined, safe and efficient pertussis vaccine.

Amino Acid Sequence↗
PubMed1990

Studies on the structural requirement for ligand binding to the neuropeptide Y (NPY) receptor from rat cerebral cortex.

Analogues of the NPY model peptide NPY 1-4-Aca-25-36 were synthesized by solid phase peptide synthesis using the tea-bag method for parallel peptide synthesis. The affinity of the peptides as ligands to the NPY receptor in rat cerebral cortex was investigated. The model compound NPY 1-4-Aca-25-36 was a relatively poor ligand to the NPY receptor in rat brain (IC50 = 0.40 microM). Arg35 and Arg33 were both important for ligand recognition by the NPY receptor. Substitutions in several positions in the region corresponding to the C-terminal part of NPY resulted in analogues with only minor reduction of the affinity for the NPY receptor.

Amino Acid Sequence↗
PubMed1990

Protective immunogenicity of two synthetic peptides selected from the amino acid sequence of Bordetella pertussis toxin subunit S1.

Two peptides, corresponding to amino acids 1-17 and 169-186 of the amino acid sequence of pertussis toxin (PT) subunit S1, were synthesized and coupled to the diphtheria toxin cross-reactive mutant protein CRM 197 and evaluated for immunogenicity and protective capacity against PT challenge in vivo. The peptide-CRM conjugates induced high antibody titers against native toxin in mice (BALB/c, C57/Black, and outbred NMRI) as measured by ELISA. Upon PT challenge (0.5 microgram of toxin) of the NMRI mice, the CRM conjugates of peptides 1-17 and 169-186 fully protected the mice from PT-induced leukocytosis. Immunization with the corresponding bovine serum albumin conjugates of these two peptides also fully protected mice. Rabbit antiserum to the peptide 1-17-CRM conjugate was highly efficient in inhibiting the ADP-ribosylating activity of PT but did not neutralize the clustering effect of PT on Chinese hamster ovary cells. In contrast, the rabbit antiserum raised against the peptide 169-186-CRM conjugate neutralized the clustering effect of PT on Chinese hamster ovary cells but did not inhibit the enzymatic activity of PT. Peptide 169-186-CRM conjugates mimic the immunoglobulin binding properties of PT and also cause clustering of Chinese hamster ovary cells. The CRM conjugates of these two peptides constitute a synthetic pertussis vaccine candidate with the ability to provide a chemically well-defined, safe, and efficient pertussis vaccine.

Amino Acid Sequence↗
PubMed1989

Galanin receptor and its ligands in the rat hippocampus.

Receptors for the 29-amino-acid peptide, galanin, in membranes from the rat ventral hippocampus were examined using chloramine-T-iodinated porcine galanin as ligand. The equilibrium binding of 125I-galanin showed the presence of a high-affinity binding site (Kd = 1.91 +/- 0.40 nM). The concentration of the high-affinity-binding sites was 107 +/- 15 fmol/mg membrane protein. The on rate constant was estimated to be 2.6 +/- 0.1 M-1 min-1 at 37 degrees C. The affinity of rat galanin (differing in three amino acid residues from the porcine protein) was equal to that of porcine galanin. The 125I--galanin-binding site is a trypsin-sensitive membrane protein, which is heat-denaturated at 60 degrees C within 5 min. The effect of GTP and its analogs and of pertussis-toxin-catalyzed ADP-ribosylation on the binding of 125I-galanin suggest that the galanin receptor is coupled to an inhibitory G protein (Gi protein). 127I-galanin was shown to be a ligand with affinity equal to that of galanin in displacing 125I-galanin. The 125I-galanin-binding site in the ventral hippocampus recognizes as a ligand the tryptic fragments 1-20 and 21-29 of rat galanin and the synthetic fragments 12-29, 18-29 and 21-29 of porcine galanin. None of these afforded full inhibition of the binding of fragment 1-29 of 125I-galanin at a concentration of 1 microM.

Animals↗