Synthesis, characterization and thermal sensitivity of chitosan-based graft copolymers

Novel chitosan-based graft copolymers (CECTS-g-PDMA) were synthesized through homogeneous graft copolymerization of (N,N-dimethylamino)ethyl methacrylate (DMA) onto N-carboxyethylchitosan (CECTS) in aqueous solution by using ammonium persulfate (APS) as the initiator. The effect of polymerization variables, including initiator concentration, monomer concentration, reaction time and temperature, on grafting percentage was studied. XRD, FTIR, DSC and TGA were used to characterize the graft copolymers. Surface-tension measurements, turbidity measurements and temperature-variable (1)H NMR analysis were combined to investigate the thermal sensitivity of CECTS-g-PDMAs in aqueous solution.     

Synthesis and characterization of photocurable elastomers from poly(glycerol-co-sebacate)

Elastomeric networks are increasingly being investigated for a variety of biomedical applications including drug delivery and tissue engineering. However, in some cases, their preparation requires the use of harsh processing conditions (e.g., high temperature), which limits their biomedical application. Herein, we demonstrate the ability to form elastomeric networks from poly(glycerol-co-sebacate) acrylate (PGSA) under mild conditions while preserving a wide range of physical properties. These networks presented a Young's modulus between 0.05 and 1.38 MPa, an ultimate strength from 0.05 to 0.50 Mpa, and elongation at break between 42% and 189% strain, by varying the degree of acrylation (DA) of PGSA. The in vitro enzymatic and hydrolytic degradation of the polymer networks was dependent on the DA. The copolymerization of poly(ethylene glycol) diacrylate with PGSA allowed for an additional control of mechanical properties and swelling ratios in an aqueous environment, as well as enzymatic and hydrolytic degradation. Photocured PGSA networks demonstrated in vitro biocompatibility as judged by sufficient human primary cell adherence and subsequent proliferation into a confluent monolayer. These photocurable degradable elastomers could have potential application for the encapsulation of temperature-sensitive factors and cells for tissue engineering.     

Synthesis and characterization of thermoset biodegradable elastomers based on star-poly(epsilon-caprolactone-co-D,L-lactide)

Biodegradable elastomers represent a useful class of biomaterials. In this paper, we synthesize thermoset elastomers by utilizing the living nature of ring-opening polymerization of a star copolymer of D,L-lactide and epsilon-caprolactone initiated with glycerol and catalyzed by stannous 2-ethylhexanoate. The star copolymers were synthesized of varying molecular weight and monomer composition and cross-linked by compression molding using a dilactone, bis(epsilon-caprolactone-4-yl)propane dissolved in epsilon-caprolactone monomer. The elastomers were then characterized by differential scanning calorimetry and uniaxial tensile testing and their physical properties related to the nature of the star copolymer prepolymers. The results demonstrate a means of predictably altering the elastomer physical properties by adjusting the star copolymer prepolymer initial molecular weight and monomer ratio.     

Synthesis, processing, and transport of Pseudomonas aeruginosa elastase.

Three cell-associated elastase precursors with approximate molecular weights of 60,000 (P), 56,000 (Pro I), and 36,000 (Pro II) were identified in Pseudomonas aeruginosa cells by pulse-labeling with [35S]methionine and immunoprecipitation. In the absence of inhibitors, cells of a wild-type strain as well as those of the secretion-defective mutant PAKS 18 accumulated Pro II as the only elastase-related radioactive protein. EDTA but not EGTA [ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid] inhibited the formation of Pro II, and this inhibition was accompanied by the accumulation of Pro I. P accumulated in cells labeled in the presence of ethanol (with or without EDTA), dinitrophenol plus EDTA, or carbonyl cyanide m-chlorophenyl hydrazone plus EDTA. Pro I and Pro II were localized to the periplasm, and as evident from pulse-chase experiments, Pro I was converted to the mature extracellular enzyme with Pro II as an intermediate of the reaction. P was located to the membrane fraction. Pro I but not Pro II was immunoprecipitated by antibodies specific to a protein of about 20,000 molecular weight (P20), which, as we showed before (Kessler and Safrin, J. Bacteriol. 170:1215-1219, 1988), forms a complex with an inactive periplasmic elastase precursor of about 36,000 molecular weight. Our results suggest that the elastase is made by the cells as a preproenzyme (P), containing a signal sequence of about 4,000 molecular weight and a "pro" sequence of about 20,000 molecular weight. Processing and export of the preproenzyme involve the formation of two periplasmic proenzyme species: proelastase I (56 kilodaltons [kDa]) and proelastase II (36 kDa). The former is short-lived, whereas proelastase II accumulates temporarily in the periplasm, most likely as a complex with the 20-kDa propeptide released from proelastase I upon conversion to proelastase II. The final step in elastase secretion seems to required both the proteolytic removal of a small peptide from proelastase II and dissociation of the latter from P20.     

Isolation and characterization of rat pancreatic elastase

Proelastase has been purified to homogeneity from rat pancreatic tissue by a combination of CM-Sephadex and immobilized protease inhibitor affinity resins. Trypsin activation yields an elastolytic enzyme that possesses a specificity toward small hydrophobic residues in synthetic amide substrates, similar to those of porcine elastase 1 and canine elastase. However, the rat enzyme also rapidly hydrolyzes a substrate containing tyrosine in the P1 position. N-Terminal sequence analysis reveals that rat proelastase has an identical activation peptide with that of porcine proelastase 1 and has two conservative amino acid sequence differences from the activation peptide of canine proelastase. The sequence data established that rat proelastase corresponds to the elastase 1 mRNA clone isolated by MacDonald et al. [MacDonald, R. J., Swift, G. H., Quinto, C., Swain, W., Pictet, R. L., Nikovits, W., & Rutter, W. J. (1982) Biochemistry 21, 1453]. The sequence and substrate data obtained for rat and canine elastases suggest that there is a family of pancreatic elastases with properties similar to those of the classically described porcine elastase 1.     

Preparation, characterization and cytocompatibility of polyurethane/cellulose based liquid crystal composite membranes

Two types of polyurethane/liquid crystal (PU/LC) composite membranes with different LC contents, namely polyurethane/octyl hydroxypropyl cellulose ester (PU/OPC) and polyurethane/propyl hydroxypropyl cellulose ester (PU/PPC), were prepared and studied. The effects of surface properties on cell compatibility of the membranes were elucidated. PPC tended to assemble to independent phases in the composite membranes, while OPC formed uniformly distributed LC domains. As the introduction of LC, phase separation occurred, and the crystallization of PU was disrupted. The surface of PU/LC composite membranes showed fingerprint texture and two-phase morphology. Hydrophilicity of the two types of composite membranes exhibited a reversal tendency with the increase of LC contents. Cells seeded on the composite membranes presented favorable growth when the content of LC was over 30%, especially on PU/OPC complex. The surface morphology, phase separation between LC and PU as well as the type of LC showed significant effects on the cell behaviors.     

Conformational characterization of designed minibarnase

We have designed a minibarnase by removing one module from barnase, a bacterial RNase from Bacillus amyloliquefaciens. Barnase, consisting of 110 amino acid residues, is decomposed into six modules, M1-M6. Module is defined as a peptide segment consisting of contiguous amino acid residues that makes a small compact conformation within a globular domain. To understand the role of module in protein architecture, we analyzed NMR and CD spectra of a minibarnase, which lacked 26 amino acid residues corresponding to module M2. We demonstrated the formation of hydrophobic cores in the minibarnase similar to those of barnase. Although its conformational stability against acids and heat was reduced in comparison with barnase, the minibarnase retained cooperative folding character (two-state folding). Therefore, the folding of the minibarnase consisting of modules M1 and M3-M6 is independent to some extent of module M2. This finding may be useful for future module-based protein design.     

Synthesis of novel mono and bis nitric oxide donors with high cytocompatibility and release activity

Four compounds bearing amidoxime functions were synthetized: (1) 2a,b bearing an aromatic amidoxime function, (2) 2c bearing an aliphatic amidoxime function, and (3) 2d bearing aromatic and aliphatic amidoximes functions. The ability of these compounds to release NO was evaluated in vitro using the oxidative metabolism of cytochrome P450 from rat liver microsomes. Results obtained demonstrate that all amidoximes were able to release NO with a highest amount of NO produced by the 2a aromatic amidoxime. Moreover, all amidoximes exhibit cytocompatibility with human aorta smooth muscle cells. Using intracellular S-nitrosothiol formation as a marker of NO bioavailability, compounds 2a–c were demonstrated to deliver a higher amount of NO in the intracellular environment than the reference. Considering that the concentration of the bis-amidoxime 2d was two times lower that than of 2a and 2b, we can assume that 2d is the most potent molecule among the tested compounds for NO release.     

Pseudomonas aeruginosa A2 elastase: purification, characterization and biotechnological applications

An extracellular protease from Pseudomonas aeruginosa A2 grown in media containing shrimp shell powder as a unique source of nutriments was purified and characterized. The enzyme was purified to homogeneity from culture supernatant by ultrafiltration, Sephadex G-100 gel filtration and Sepharose Mono Q anion exchange chromatography, with a 2.23-fold increase in specific activity and 64.3% recovery. The molecular mass of the enzyme was estimated to be 34 kDa. Temperature and pH with highest activity were 60 °C and 8.0, respectively. The protease activity was inhibited by EDTA suggesting that the purified enzyme is a metalloprotease. The enzyme is stable in the presence of organic solvents mainly diethyl ether and DMSO. The lasB gene, encoding the A2 elastase, was isolated and its DNA sequence was determined. The A2 protease was tested for shrimp waste deproteinization in the process of chitin preparation. The percent of protein removal after 3 h hydrolysis at 40 °C with an enzyme/substrate (E/S) ratio of 5 U/mg protein was about 75%. Additionally, A2 proteolytic preparation demonstrated powerful depilating capabilities of hair removal from bovine skin. Considering its promising properties, P. aeruginosa A2 protease may be considered a potential candidate for future use in several biotechnological processes.     

Identification of elastase in human eosinophils: immunolocalization, isolation, and partial characterization.

Although an elastolytic activity in eosinophil-rich cell fractions from mice has been reported, this enzyme has not been purified and characterized as yet in any mammalian species. Eosinophilic elastase was isolated from human eosinophil fragments (cytosomes) obtained from normal and eosinophilic subjects. The enzyme was purified to apparent electrophoretic homogeneity by fast protein liquid chromatography. The enzyme shows the same physical properties of the major elastase isoenzyme of human neutrophils. In addition, like monocyte elastase, it reacts with a monoclonal antibody against human neutrophil elastase. The biochemical similarities observed between the above-mentioned enzymes and the immunolocalization findings strongly support the idea that human eosinophils and neutrophils contain the same enzyme activity. Eosinophils show immunoreactive material in both types of dense cytoplasmic granules. This observation supports the current hypothesis that the different types of eosinophilic granules represent successive morphological stages of maturation.     

Purification, identification, and characterization of elastase on erythrocyte membrane as factor IX-activating enzyme

In our previous papers, we reported that factor IX (F-IX), when activated by erythrocyte membranes, causes coagulation. We report on purification, identification, and characterization of F-IX-activating enzyme extracted from human erythrocyte membranes. The enzyme whose amino acid sequence is almost in accord with neutrophil elastase was found in normal erythrocyte membrane. The molecular mass was slightly smaller than that of neutrophil elastase. The content of the enzyme in erythrocyte membranes was estimated to be 3.0-3.7 ng per 10(6)erythrocytes. The F-IX sites cleaved by the enzyme were slightly different from those by the ordinary coagulation reaction. The ability of F-IX cleaved by the enzyme to cause coagulation was estimated to be approximately 1/10 as high as that of the F-IX cleaved by activated F-XI. These findings provide evidence that F-IX is activated by erythrocyte membrane, which may serve as a triggering mechanism for blood coagulation.     

Identification and characterization of trypsin, chymotrypsin and elastase inhibitors in porcine serum.

Characterization of the trypsin-, chymotrypsin- and elastase-inhibiting properties of porcine serum was carried out by gel filtration on Ultrogel, AcA 44, and agarose gel electrophoresis with subsequent processing for protease-inhibiting activity. Moreover, by allowing the fractions obtained from gel filtration to react with antibodies to porcine serum protease inhibitors, the specific inhibiting properties of these inhibitor molecules were identified. At least six protease inhibitors were identified and partially characterized in porcine serum. Two alpha 2 -macroglobulins (alpha 2 Mf and alpha 2 Ms), homologues to human alpha 2 -macroglobulin, with slightly different electrophoretic mobilities, were both found to exhibit trypsin, chymotrypsin and elastase inhibiting activity. Alpha 1 -Protease inhibitor (Mr 51 000), a homologue to human alpha 1 -protease inhibitor (alpha 1 -antitrypsin), also showed trypsin-, chymotrypsin- and elastase-inhibiting properties. Inter-alpha-trypsin inhibitor (Mr 162 000 and 129000), a porcine serum counterpart to human inter-alpha-trypsin inhibitor, showed trypsin- and chymo-trypsin-inhibiting properties. In addition, a specific trypsin inhibitor, alpha 2 -antigrypsin (Mr 58 000), and a specific elastase inhibitor, beta-elastase inhibitor, were characterized in porcine serum, and these seem to have no counterparts in human serum.     

The elastase inhibitors of swine serum: isolation and partial characterization of the beta 1-globulin inhibitor and its interaction with elastase

1. The principal elastase inhibitor of swine serum, a beta 1-globulin, has been isolated from serum by ammonium sulfate fractionation, DEAE-cellulose column chromatography and chromatofocusing. 2. The purified beta 1-globulin was homogeneous by immunoelectrophoresis and sodium dodecyl sulfate polyacrylamide gel electrophoresis. Multiple zones (isoinhibitors) were produced on anionic polyacrylamide gels. The mol. wt for the native, elastase-inactivated inhibitor and the beta 1-globulin-elastase complex were respectively, 65,467 and 60,000 and 79,667. The amino acid residue weight was 63,331. 4. The electrophoretic mobilities of the native inhibitor, elastase-inactivated inhibitor and the inhibitor-elastase complex were respectively, -3.4, -3.8 and -2.2 x 10(-5) cm2/V per sec, the isoelectric points were respectively, 4.78-5.28 (major pIs = 5.15, 5.35), 4.63-5.35 (major pI = 5.13) and 6.02-6.2 (major pI = 6.12). 5. The first order dissociation rate constant for the beta 1-globulin-elastase complex (two-fold molar excess of elastase at 37 degrees C) was 1.9 x 10(-3) per sec with complete dissociation in 40.4 min. The dissociation constant for the complex was 1.47 x 10(-7) M. One mol of elastase was bound per mol of the inhibitor. 6. The beta 1-globulin-elastase complex reacts with antibody to either protein moiety.     

Cloning, expression and characterization of recombinant elastase from Pseudomonas aeruginosa in Picha pastoris

The gene lasB from Pseudomonas aeruginosa, which encoded elastase, was cloned and firstly successfully expressed in Pichia pastoris stain KM71 under the control of AOX promoter. The effects on the recombinant elastase activities of different pH, different temperatures and different metal ions were assayed. The full-length gene (1497 bp) encodes a preproenzyme including an N-terminal signal peptide (23 aa), a propeptide (197 aa) and mature elastase (301 aa). The recombinant elastase was secreted into culture supernatants using signal sequence from lasB and showed a single band at about 34 kDa by SDS-PAGE. The recombinant elastase expression hit the highest level of approximately 450 mg/L and the specific elastolytic activity of the recombinant elastase was 130 U/ml, which was approximately 26-fold higher than that of elastase obtained from P. aeruginosa. The optimal temperature and pH of the recombinant elastase was 28 degrees C and 7.4, respectively. The enzyme possessed high resistance to heat, and can be activated by Ca(2+). These enzyme properties suggested that it could be produced in an industrial scale and has the potential to be a commercial enzyme.     

嗜水气单胞菌J-1株弹性蛋白酶的表达、纯化及特性分析

摘要：【目的】表达、纯化嗜水气单胞菌J-1株弹性蛋白酶,并对弹性蛋白酶的性质进行分析。【方法】以pET-32a为表达载体将弹性蛋白酶基因ahyB转化至大肠杆菌BL21菌株中进行诱导表达,表达重组酶用His TaqNi2+亲和层析柱纯化并用6 mol/L盐酸胍进行复性;利用硫酸铵分级沉淀、阴离子交换层析和分子筛层析对嗜水气单胞菌培养上清液中的弹性蛋白酶进行纯化。将【结果】从嗜水气单胞菌培养上清液中获得的弹性蛋白酶原酶的最适pH 为8.5,而表达重组酶为 10.0;对热的稳定性,原酶高于表达酶。两种形式酶的性     

Partial purification and characterization of mouse peritoneal exudative macrophage elastase

Mouse peritoneal exudate macrophage elastase can be significantly purified with 60% recovery of the starting activity by affinity chromatography against SDS-treated alpha-elastin covalently linked to agarose beads. The enzyme has an apparent Mr of 26 500 based on SDS-acrylamide gel electrophoresis. Molecular sieving chromatography on Sephadex gel gives a Mr for macrophage elastase of 21 000--28 000. The enzyme is not inhibited by chloromethyl ketone inactivators specific for pancreatic and leukocyte elastase nor by phenylmethylsulfonyl fluoride. Macrophage elastase also does not bind to tritiated diisopropylphosphorofluoridate. The enzyme is inhibited by EDTA and thus appears to be a metallo-protease. Macrophage elastase is resistant to human alpha 1-proteinase inhibitor and to human and mouse alpha 2-macroglobulin. In view of its lack of susceptibility to these endogenous serum proteinase inhibitors, macrophage elastase may play an important role in physiological and pathological remodeling of connective tissues.     

Cloning and characterization of elastase genes from Pseudomonas aeruginosa.

A gene bank was constructed from Pseudomonas aeruginosa PAO1 and used to complement three P. aeruginosa elastase-deficient strains. One clone, pRF1, contained a gene which restored elastase production in two P. aeruginosa isolates deficient in elastase production (PA-E15 and PAO-E105). This gene also encoded production of elastase antigen and activity in Escherichia coli and is the structural gene for Pseudomonas elastase. A second clone, pHN13, contained a 20-kilobase (kb) EcoRI insert which was not related to the 8-kb EcoRI insert of pRF1 as determined by restriction analysis and DNA hybridization. A 2.2-kb SalI-HindIII fragment from pHN3 was subcloned into pUC18, forming pRB1822-1. Plasmid pRB1822-1 restored normal elastolytic activity to PAO-E64, a mutant for elastase activity. Clones derived from pHN13 failed to elicit elastase antigen or enzymatic activity in E. coli.     

Synthesis, processing and degradation in yeast of precursor human lysozyme with newly designed signal sequences

Recently, we reported that the synthesis of human lysozyme in yeast is inhibited when artificially designed non-native signal sequences are used [Yamamoto et al. (1987) Biochem. Biophys. Res. Commun. 149, 431-436; (1989) Biochemistry 28, 2728-2732]. Pulse/chase experiments described in the present paper have now revealed that precursor lysozymes are actually synthesized with these signal sequences, but that they are spontaneously degraded, suggesting that the enzyme is destabilized by the signal sequences. The data further show a good correlation between the secretory capability of the artificial signal sequences and the efficiency of the processing of precursor lysozyme.     

Synthesis and evaluation of bidentate ligands designed to interact with PDZ domains

We designed bidentate ligands to target PDZ domains through two binding sites: site S0, delimited by the GLGF loop, and site S1, a zone situated around loop β(B)/β(C). A molecular docking study allowed us to design a generic S0 binder, to which was attached a variable size linker, itself linked to an amino acid aimed to interact with the S1 site of PDZ domains. A series of 15 novel bidentate ligands was prepared in 6-11 steps in good overall yield (24-43%). Some of these ligands showed an inhibitory activity against serotonin 5-HT2A receptor/PSD-95 interaction. This was assessed by pull-down assay using a synthetic decapeptide corresponding to the C-terminal residues of the receptor as a bait.     

Human leukocyte granule elastase: rapid isolation and characterization.

Human granulocytic elastases have been purified by a two-step procedure involving affinity chromatography of crude extracts of leukocytic granules on Sepharose-Trasylol, followed by ion-exchange chromatography on CM-cellulose to resolve the isoelastases. All of these enzymes were found to be glycoproteins with the carbohydrate content of the major form being composed essentially of only neutral sugars. The molecular weight of this form was found to be near 30 000 daltons with the other forms being slightly higher. Preliminary structural analyses indicate that all of the elastase isozymes have identical NH2-terminal sequences suggesting that the differences in mobility of the four proteins are not due to different degrees of activation from a common zymogen but, more likely, from minor changes in carbohydrate content. Human granulocytic elastases are less active on ligament elastin than porcine pancreatic elastase, but both are inhibited by synthetic elastase active-site directed low molecular weight compounds (Tuhy, P. M., and Powers, J. C. (1975), FEBS Lett. 50, 359) as well as by plasma alpha-1-proteinase inhibitor (formerly called alpha-1-antitrypsin). In the latter case a stable complex with mol wt of 78 000 daltons is formed indicating the formation of a 1:1 complex.