Improved synthesis of hyaluronic acid hydrogel and its effect on tissue augmentation.

HA-HMDA hydrogels were developed by direct amide bond formation between the carboxyl groups of hyaluronic acid (HA) and hexamethylenediamine (HMDA) with an optimized carboxyl group modification in the preliminary experiment. However, these HA-HMDA hydrogels transformed into an unstable liquid form after steam sterilization, and were problematic for application to actual dermal filler. A new method to overcome the problem of the previously developed HA-HMDA hydrogels is to prepare them by adjusting the pH in this study. Not only are these improved HA-HMDA hydrogels prepared with lower amounts of cross-linking and activation agents compared to the previously developed hydrogels, but they also maintain a stable form after steam sterilization. These improved HA-HMDA hydrogels showed higher viscoelasticity and longer lasting effects than the previous ones, despite the fact that the amount of the HMDA used as a cross-linking agent as well as 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and 1-hydroxybenzotriazole monohydrated (HOBt) used as activation agents were substantially reduced. According to an in vivo test using a wrinkled mouse model, the improved HA-HMDA hydrogels exhibited significantly improved tissue augmentation effects compared to a positive control of Restylane, which is widely used for the tissue augmentation throughout the world. Furthermore, histological analysis revealed excellent biocompatibility and safety of the improved synthesized HA-HMDA hydrogels.

Effect of cross-linking reagents for hyaluronic acid hydrogel dermal fillers on tissue augmentation and regeneration.

A novel, biocompatible, and nontoxic dermal filler using hyaluronic acid (HA) hydrogels was successfully developed for tissue augmentation applications. Instead of using highly reactive cross-linkers such as divinyl sulfone (DVS) for Hylaform, 1,4-butanediol diglycidyl ether (BDDE) for Restylane, and 1,2,7,8-diepoxyoctane (DEO) for Puragen, HA hydrogels were prepared by direct amide bond formation between the carboxyl groups of HA and hexamethylenediamine (HMDA) with an optimized carboxyl group modification for effective tissue augmentation. The HA-HMDA hydrogels could be prepared within 5 min by the addition of HMDA to HA solution activated with 1-ethyl-3-[3-(dimethylamino)propyl]carbodiimide (EDC) and 1-hydroxybenzotriazole monohydrate (HOBt). Five kinds of samples, a normal control, a negative control, a positive control of Restylane, adipic acid dihydrazide grafted HA (HA-ADH) hydrogels, and HA-HMDA hydrogels, were subcutaneously injected to wrinkled model mice. According to the image analysis on dorsal skin augmentation, the HA-HMDA hydrogels exhibited the best tissue augmentation effect being stable longer than 3 months. Furthermore, histological analyses after hematoxylin-eosin (H&E) and Masson's trichrome staining revealed the excellent biocompatibility and safety of HA-HMDA hydrogels. The dermal thickness and the dermal collagen density in wrinkled mice after treatment with HA-HMDA hydrogels for 12 weeks were comparable to those of normal mice. Compared with HA-DVS hydrogels and Restylane, the excellent tissue augmentation by HA-HMDA hydrogels might be ascribed to the biocompatible residues of amine groups in the cross-linker of HMDA. The HA-HMDA hydrogels will be investigated further as a novel dermal filler for clinical applications.

Characterization of heat-labile uracil-DNA glycosylase from Psychrobacter sp. HJ147 and its application to the polymerase chain reaction.

The gene encoding Psp HJ147 UDG (Psychrobacter sp. HJ147 uracil-DNA glycosylase) was cloned and sequenced. The gene consists of 735 bp for coding a protein with 244 amino acid residues. The deduced amino acid sequence of Psp HJ147 UDG showed a high similarity to that of Psychrobacter articus, Psychrobacter cryohalolentis K5 and Psychrobacter sp. PRwf-1. The PCR-amplified Psp HJ147 UDG gene was expressed under the control of the T7lac promoter on pTYB1 in Escherichia coli BL21(DE3). The expressed enzyme was purified with IMPACT-CN (intein-mediated purification with an affinity chitin-binding tag) system. The optimum pH and temperature of the purified enzyme were 7.0-7.5 and 20-25 degrees C respectively. The optimum NaCl and KCl concentrations for the activity of the purified enzyme ranged from 50 to75 mM. The half-life of the enzyme at 50 degrees C was approx. 45 s. These heat-labile characteristics enabled Psp HJ147 UDG to control carry-over contamination in direct PCR without loss of the PCR product. Psp HJ147 UDG's contaminant control in both direct PCR and indirect PCR exhibited superiority over the UDG of the marine psychrophilic bacterium strain BMTU 3346 and that of E. coli.

Novel DNA ligase with broad nucleotide cofactor specificity from the hyperthermophilic crenarchaeon Sulfophobococcus zilligii: influence of ancestral DNA ligase on cofactor utilization.

DNA ligases are divided into two groups according to their cofactor requirement to form ligase-adenylate, ATP-dependent DNA ligases and NAD(+)-dependent DNA ligases. The conventional view that archaeal DNA ligases only utilize ATP has recently been disputed with discoveries of dual-specificity DNA ligases (ATP/ADP or ATP/NAD(+)) from the orders Desulfurococcales and Thermococcales. Here, we studied DNA ligase encoded by the hyperthermophilic crenarchaeon Sulfophobococcus zilligii. The ligase exhibited multiple cofactor specificity utilizing ADP and GTP in addition to ATP. The unusual cofactor specificity was confirmed via a DNA ligase nick-closing activity assay using a fluorescein/biotin-labelled oligonucleotide and a radiolabelled oligonucleotide. The exploitation of GTP as a catalytic energy source has not to date been reported in any known DNA ligase. This phenomenon may provide evolutionary evidence of the nucleotide cofactor utilization by DNA ligases. To bolster this hypothesis, we summarize and evaluate previous assertions. We contend that DNA ligase evolution likely started from crenarchaeotal DNA ligases and diverged to eukaryal DNA ligases and euryarchaeotal DNA ligases. Subsequently, the NAD(+)-utilizing property of some euryarchaeotal DNA ligases may have successfully differentiated to bacterial NAD(+)-dependent DNA ligases.

Mutational analysis of Thermus caldophilus GK24 beta-glycosidase: role of His119 in substrate binding and enzyme activity.

Three amino acid residues (His119, Glu164, and Glu338) in the active site of Thermus caldophilus GK24 beta- glycosidase (Tca beta-glycosidase), a family 1 glycosyl hydrolase, were mutated by site-directed mutagenesis. To verify the key catalytic residues, Glu164 and Glu338 were changed to Gly and Gln, respectively. The E164G mutation resulted in drastic reductions of both beta-galactosidase and beta-glucosidase activities, and the E338Q mutation caused complete loss of activity, confirming that the two residues are essential for the reaction process of glycosidic linkage hydrolysis. To investigate the role of His119 in substrate binding and enzyme activity, the residue was substituted with Gly. The H119G mutant showed 53-fold reduced activity on 5 mM p-nitrophenyl beta-Dgalactopyranoside, when compared with the wild type; however, both the wild-type and mutant enzymes showed similar activity on 5 mM p-nitrophenyl beta-D-glucopyranoside at 75degreeC. Kinetic analysis with p-nitrophenyl beta-D-galactopyranoside revealed that the kcat value of the H119G mutant was 76.3-fold lower than that of the wild type, but the Km of the mutant was 15.3-fold higher than that of the wild type owing to the much lower affinity of the mutant. Thus, the catalytic efficiency (kcat/Km) of the mutant decreased to 0.08% to that of the wild type. The kcat value of the H119G mutant for p-nitrophenyl beta- D-glucopyranoside was 5.1-fold higher than that of the wild type, but the catalytic efficiency of the mutant was 2.5% of that of the wild type. The H119G mutation gave rise to changes in optima pH (from 5.5-6.5 to 5.5) and temperature (from 90 degrees C to 80-85 degrees C). This difference of temperature optima originated in the decrease of H119G's thermostability. These results indicate that His119 is a crucial residue in beta- galactosidase and beta-glucosidase activities and also influences the enzyme's substrate binding affinity and thermostability.

Cloning and expression of a DNA ligase from the hyperthermophilic archaeon Staphylothermus marinus and properties of the enzyme.

The gene encoding Staphylothermus marinus DNA ligase (Sma DNA ligase) was cloned and sequenced. The gene contains an open reading frame consisting of 1836bp, which encodes for 611 amino acid residues. Upon alignment of the entire amino acid sequence, Sma DNA ligase showed a high degree of sequence homology with the hyperthemophilic archaeal DNA ligases, 67% identity with Aeropyrum pernix K1, and 40% identity with both Pyrococcus abyssi and Thermococcus kodakarensis. An extremely high sequence identity was observed in the six conserved motifs indicative of DNA ligase. The Sma DNA ligase gene was expressed under the control of the T7lac promoter on the pET-22b(+) in Escherichia coli BL21-CodonPlus(DE3)-RIL. The expressed enzyme was then purified by heat treatment followed by ion exchange and metal affinity column chromatography. The enzyme was activated by both Mg(2+) and Mn(2+), and its activity was inhibited by Ca(2+) and Zn(2+). Sma DNA ligase can utilize both ATP and ADP as cofactors. The half-life of the enzyme at 100 degrees C was determined to be approximately 2.8h. The enzyme catalyzed cohesive-end intramolecular and intermolecular joining and blunt-end intermolecular joining in the presence of tricine-NaOH buffer and Mn(2+), using either ATP or ADP.