Biomedical subjects

M Jasionowski

Publications and source records attributed to M Jasionowski.

6 recordsLinked to original sources

PubMed2001

Injectable gels for tissue engineering.

Recently, tissue engineering approaches using injectable, in situ gel forming systems have been reported. In this review, the gelation processes and several injectable systems that exhibit in situ gel formation at physiological conditions are discussed. Applications of selected injectable systems (alginate, chitosan, hyaluronan, polyethylene oxide/polypropylene oxide) in tissue engineering are also described. Injectable polymer formulation can gel in vivo in response to temperature change (thermal gelation), pH change, ionic cross-linking, or solvent exchange. Kinetics of gelation is directly affected by its mechanism. Injectable formulations offer specific advantages over preformed scaffolds such as: possibility of a minimally invasive implantation, an ability to fill a desired shape, and easy incorporation of various therapeutic agents. Several factors need to be considered before an injectable gel can be selected as a candidate for tissue engineering applications. Apart from tissue-specific cell-matrix interactions, the following gel properties need to be considered: gelation kinetics, matrix resorption rate, possible toxicity of degradation products and their elimination routes, and finally possible interference of the gel matrix with histogenesis.

Alginates↗

PubMed1999

Copper(II) complexation by pituitary adenylate cyclase activating polypeptide fragments.

Results are reported from potentiometric and spectroscopic (UV-Vis, CD, and ESR) studies of the protonation constants and Cu2+ complex stability constants of pituitary adenylate cyclase activating polypeptide fragments (HSDGI-NH2, TDSYS-NH2, RKQMAVKKYLAAVL-NH2). With HSDGI-NH2, the formation of a dimeric complex Cu2H-2L2 was found in the pH range 5-8, in which the coordination of copper(II) is glycylglycine-like, while the fourth coordination site is occupied by the imidazole N3 nitrogen atom, forming a bridge between two copper(II) ions. The formation of dimeric species does not prevent the deprotonation and coordination of the amide nitrogen, and in pH above 8 the CuH-2L complex is formed. Aspartic acid in the third position of peptide sequence stabilizes the CuH-2L species and prevents the coordination of a fourth nitrogen donor. Aspartic acid residue in the second position of TDSYS-NH2 stabilizes the CuL (2N) complex but does not prevent deprotonation and binding of the second and third peptide nitrogens to give 3N and 4N complexes at higher pH. The tetradecapeptide amide forms with copper(II) ions unusually stable 3N and 4N complexes compared to pentaalanine amide.

Amino Acid Sequence↗

PubMed1999

Constitutive and regulated alpha-secretase cleavage of Alzheimer's amyloid precursor protein by a disintegrin metalloprotease.

Amyloid beta peptide (Abeta), the principal proteinaceous component of amyloid plaques in brains of Alzheimer's disease patients, is derived by proteolytic cleavage of the amyloid precursor protein (APP). Proteolytic cleavage of APP by a putative alpha-secretase within the Abeta sequence precludes the formation of the amyloidogenic peptides and leads to the release of soluble APPsalpha into the medium. By overexpression of a disintegrin and metalloprotease (ADAM), classified as ADAM 10, in HEK 293 cells, basal and protein kinase C-stimulated alpha-secretase activity was increased severalfold. The proteolytically activated form of ADAM 10 was localized by cell surface biotinylation in the plasma membrane, but the majority of the proenzyme was found in the Golgi. These results support the view that APP is cleaved both at the cell surface and along the secretory pathway. Endogenous alpha-secretase activity was inhibited by a dominant negative form of ADAM 10 with a point mutation in the zinc binding site. Studies with purified ADAM 10 and Abeta fragments confirm the correct alpha-secretase cleavage site and demonstrate a dependence on the substrate's conformation. Our results provide evidence that ADAM 10 has alpha-secretase activity and many properties expected for the proteolytic processing of APP. Increases of its expression and activity might be beneficial for the treatment of Alzheimer's disease.

ADAM Proteins↗

PubMed1998

Identification of binding domains of pituitary adenylate cyclase activating polypeptide (PACAP) for its type 1 receptor by photoaffinity labeling.

Structure-function studies and photoaffinity labeling experiments were performed to identify residues and domains of PACAP involved in the interaction with PACAP receptors. For this purpose, a series of photoreactive analogues of PACAP(1-27) containing a photoreactive benzophenone (BP) residue in different peptide structural domains were utilized to analyze the interaction of PACAP(1-27) with pig PACAP type 1 receptors. Five PACAP derivatives were created with a photoreactive amino acid in the following peptide domains: either the disordered N-terminal or the helical C-terminal domain or a short loop region within the C-terminal helical domain of the peptide. Their receptor binding properties and efficiencies were tested on pig brain PACAP receptors. The results indicate the importance of the helical C-terminal domain of PACAP(1-27) for receptor binding affinity. Monoiodination of the photoreactive analogues did not change their binding affinities. Experiments with pig brain membranes demonstrated that the 125I-labeled photoreactive analogues specifically label a protein band of M(r) 66,000. The efficiency of photoreactive labeling differed for the various analogues. These findings suggest that Tyr22 and Lys15 in PACAP (1-27) are located in or close to the hormone binding site of the PACAP type 1 receptor. The results provide evidence that the alpha-helical C-terminal region of PACAP is directly involved in receptor binding.

Amino Acid Sequence↗

PubMed1997

Photoaffinity labeling analysis of the interaction of pituitary adenylate-cyclase-activating polypeptide (PACAP) with the PACAP type I receptor.

To identify residues and domains of the peptide hormone pituitary adenylate-cyclase-activating polypeptide (PACAP) that interact with the type I receptor, two photoreactive analogues of PACAP-(1-27)-peptide were synthesized using solid-phase peptide synthesis. Phe6 or Tyr22 within the PACAP sequence were replaced by p-benzoyl-L-phenylalanine (Bz-Phe) thus creating two PACAP derivatives with a photoreactive amino acid in either the disordered N-terminal or the helical C-terminal part of the peptide. The ligand-binding properties and the efficiencies of these peptide analogues as photolabels were tested for pig brain PACAP receptors. [Bz-Phe6]-PACAP-(1-27)-peptide (Kd 1.3 nM) retained the high binding affinity of PACAP-(1-27)-peptide (Kd 0.5 nM), wheras Bz-Phe substitution of Tyr22 reduced the affinity about tenfold (Kd 4.4 nM) thus demonstrating the importance of Tyr22 for receptor binding. Monoiodination of the photoreactive analogues did not change the binding affinity of the photoreactive analogues. Photoaffinity labeling using pig brain membrane demonstrated that the 125I-labeled photoreactive analogues specifically label a 66000-Mr protein band. Photoaffinity labeling of the rat brain PACAP receptor expressed in COS cells resulted in two specifically photolabeled proteins: a major band of Mr 58000 and a minor band of Mr 78000. By treatment of photolabeled membranes with N-glycosidase F, both of the polypeptide bands were converted to a single polypeptide band of Mr 54000, which corresponds to the deglycosylated PACAP receptor. Despite its lower receptor affinity, [Bz-Phe22]-PACAP-(1-27)-peptide labeled the PACAP type I receptor in pig brain membranes and the rat receptor expressed in COS cells with much higher efficiency (20-fold for the pig receptor) than [Bz-Phe6]-PACAP-(1-27)-peptide. These findings suggest that Tyr22 in PACAP-(1-27)-peptide is located in or close to the hormone-binding site of the PACAP type I receptor. The results provide evidence that the alpha-helical C-terminal region of PACAP is directly involved in receptor binding.

Affinity Labels↗

PubMed1995

Specific binding of Cu(II) ions by leucine-enkephalin analogs.

Results are reported from a potentiometric and spectroscopic (UV-visible, CD, and ESR) of the protonation constants and Cu(II)-complex stability constants of leucine enkephalin amide (H-Tyr-Gly-Gly-Phe-Leu-NH2, Leu-EN-amide) and two nitro analogs having 4-nitro substituent on the phenyl ring of the Phe residue, (H-Tyr-Gly-Gly-Phe(NO2)-LeuNH2, Leu-EN(nitro)- amide) and the other one with a sarcosine residue replacing the Gly3 residue (Leu-ENSar-amide). Over the pH range of 6-8.5, Leu-EN-amide interacts more strongly with Cu(II) than does the methionine analog, forming a more stable complex with three nitrogens coordinated. The Sar residue acts as a "breakpoint" to the formation of 3N or 4N complexes and, as a result, causes the formation of dimeric complexes bonded through the amino-N, a deprotonated peptide-N- and deprotonated Tyr-O- donors.

Amino Acid Sequence↗