Enhancing oxidative resistance of Agrobacterium radiobacter N-carbamoyl D-amino acid amidohydrolase by engineering solvent-accessible methionine residues

N-Carbamoyl D-amino acid amidohydrolase (D-NCAase) that catalyzes the stereospecific hydrolysis of N-carbamoyl D-amino acids to their corresponding D-amino acids is valuable in pharmaceutical industry. Agrobacterium radiobacter D-NCAase is sensitive to oxidative damage by hydrogen peroxide. To investigate the role of methionine residues in oxidative inactivation, each of the nine methionine residues in A. radiobacter D-NCAase was substituted with leucine, respectively, by site-directed mutagenesis. Except for two mutants (Met5Leu and Met31Leu) with similar activities, seven mutants (Met73Leu, Met167Leu/Met169Leu, Met184Leu, Met220Leu, Met239Leu, Met244Leu, and Met239Leu/Met244Leu) were found to have reduced activities. In the presence of H(2)O(2), three mutants (Met239Leu, Met244Leu, and Met239Leu/Met244Leu) with substitution of highly solvent-accessible methionines by leucines retained their activities. The other mutants were also considerably resistant to chemical oxidation than was the wild-type enzyme. Thus, substitution of solvent-accessible methionine residues with leucine to enhance oxidative stability of D-NCAase is practical but might be with compromised activity.

PCR with sequence-specific primer-based simultaneous genotyping of human platelet antigen-1 to -13w

BACKGROUND

Accurate human platelet antigen (HPA) typing is important for patients with diagnosis of alloimmune thrombocytopenic syndromes and provision of HPA-matched blood components for these patients.

STUDY DESIGN AND METHODS

Thirteen sequence-specific primers (SSPs) designed on the basis of known published polymorphisms for HPA-1 to HPA-13w, respectively, were employed for simultaneous HPA genotyping. All PCR amplifications were carried out with identical cycling conditions in 96-well plates containing primer mixtures. A total of 300 blood samples from unrelated volunteer donors in Taiwan were included in the study.

RESULTS

All primers had specific amplification products. The typing results were available within 4 hours each time for up to four blood samples tested. Among the 13 HPAs, HPA-3 had the greatest heterozygosity with a gene frequency of 0.3267, 0.4967, and 0.1767 for HPA-3a/HPA-3a, HPA-3a/HPA-3b, and HPA-3b/HPA3-b, respectively. For the remaining 12 HPAs, the predominance of a/a homozygosity was noted for HPA-1, -2, -4, -5, and -6, with a frequency ranging from 0.9200 to 0.9967. The frequency of a/a homozygosity was 1.0000 for HPA-7w to -13w, except for HPA-10w, for which one case was observed to be HPA-10aw/HPA-10bw heterozygous. Excluding HPA-3, b/b homozygosity was noted in only one case (HPA-6b/HPA-6b). The prevalence rates of HPA-1 to -13w in this study were consistent with previous reports using different methods.

CONCLUSION

An extended, streamlined PCR-SSP protocol for simultaneous genotyping of HPA-1 to HPA-13w was established. This allows fast and reliable diagnosis of alloimmune thrombocytopenia, and is readily applicable to large-scale genetic population studies.

Purification, characterization, and genetic analysis of a leucine aminopeptidase from Aspergillus sojae

Extracellular leucine aminopeptidase (LAP) from Aspergillus sojae was purified to protein homogeneity by sequential fast protein liquid chromatography steps. LAP had an apparent molecular mass of 37 kDa, of which approximately 3% was contributed by N-glycosylated carbohydrate. The purified enzyme was most active at pH 9 and 70 degrees C for 30 min. The enzyme preferentially hydrolyzed leucine p-nitroanilide followed by Phe, Lys, and Arg derivatives. The LAP activity was strongly inhibited by metal-chelating agents, and was largely restored by divalent cations like Zn(2+) and Co(2+). The lap gene and its corresponding cDNA fragment of the A. sojae were cloned using degenerated primers derived from internal amino acid sequences of the purified enzyme. lap is interrupted by three introns and is transcribed in a 1.3-kb mRNA that encodes a 377-amino-acid protein with a calculated molecular mass of 41.061 kDa. The mature LAP is preceded by a leader peptide of 77 amino acids, predicted to include an 18-amino-acid signal peptide and an extra sequence of 59 amino acids. Two putative N-glycosylation sites are identified in Asn-87 and Asn-288. Southern blot analysis suggested that lap is a single-copy gene in the A. sojae genome. The deduced amino acid sequence of A. sojae LAP shares only 11-33.1% identity with those of LAPs from 18 organisms.

Use of biological activated carbon to treat mixed gas of toluene and benzene in biofilter

The biodegradation of toluene and benzene in a biofilter filled with cylindrical activated carbon was studied. Three various gaseous flow rates, i.e. 0.25, 0.50 and 0.75 m3 h(-1), corresponding to empty bed gas residences of 75, 37.5 and 25 s, respectively, and total organic load lower than 400 g m(-1) h(-1) were tested. The biofilter proved to be highly efficient in biodegradations of toluene and benzene, and toluene was more easily degraded than benzene. When each inlet load of toluene and benzenewas lower than 150 g m(-3) h(-1), removal rate increased with inlet loads and reached maximum values of 150 and 120 g m(-3) h(-1) for toluene and benzene, respectively. For inlet load higher than the maximum removal capacity conditions, the removal rate decreased with inlet load. The carbon dioxide concentration profile through the biofilter revealed that the mass ratios of carbon dioxide produced to the toluene and benzene removed were 2.15 g CO2 g(-1) toluene and 1.67 g CO2 g(-1) benzene. Model predictions for toluene, benzene and carbon dioxide concentration gradient profiles were in agreement with experimental data for the tested conditions. The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of them spore baxillus was dominant.

Biological treatment characteristics of benzene and toluene in a biofilter packed with cylindrical activated carbon

The biodegradation of toluene and benzene in a biofilter using cylindrical activated carbon as the filler materials was studied. Three gas low rates, i.e. 0.25, 0.50 and 0.75 m3/h, corresponding to empty bed gas residence of 75, 37.5 and 25 s, respectively, and total organic load lower than 400 g/m3 x h were tested. The biofilter proved to be highly efficient in biodegradation of toluene and benzene, and toluene was more easily degraded than benzene. When each inlet load was lower than 150 g/m3 x h, removal rate increased with inlet load and reached a maximum, which was 150 and 120 g/m(-3) x h for toluene and benzene, respectively. For inlet load higher than the maximum removal capacity conditions, the removal rate decreased with inlet load. Carbon dioxide concentration profile through the biofilter revealed that the mass ratios of carbon dioxide produced to the toluene and benzene removed were 2.15 g(CO2)/g(toluene) and 1.67 g(CO2)/g(benzene), which furthermore, confirmed the biodegradation performance in biofilter. The observation of biotic community demonstrated that the microbes consisted of bacillus, spore bacillus and fungi, of which the spore bacillus was dominant.

Structural and redox properties of the leaderless DsbE (CcmG) protein: both active-site cysteines of the reduced form are involved in its function in the Escherichia coli periplasm

The thiol/disulfide oxidoreductases play important roles in ensuring the correct formation of disulfide bonds, of which the DsbE protein, also called CcmG, is the one implicated in electron transfer for cytochrome c maturation in the periplasm of Escherichia coli. The soluble, N-terminally truncated DsbE was overexpressed and purified to homogeneity. Here we report the structural and redox properties of the leaderless form (DsbEL-). During the redox reaction, the protein undergoes a structural transformation resulting in a more stable reduced form, but this form shows very low reactivity in thiol/ disulfide exchange of cysteine residues and low activity in accelerating the reduction of insulin. The standard redox potential (E'0) for the active thiol/ disulfide was determined to be -0.186 V; only one of the two cysteines (Cys80) was suggested to be the active residue in the redox reaction. From the aspect of biochemical properties, DsbE can be regarded as a weak reductant in the Escherichia coli periplasm. This implies that the function of DsbE in cytochrome c maturation can be ascribed to its active-site cysteines and the structure of the reduced form.

Analytical precision and repeatability of respiratory quinones for quantitative study of microbial community structure in environmental samples

Microbial community structure is one of the important factors controlling the pollutant-degrading capacity of ecosystems. The analysis of microbial quinones has gained increased recognition as a simple and useful approach for studying microbial structure in environmental samples. The analytical precision of quinone characterization using high performance liquid chromatograph (HPLC) with a UV-detector was studied in this study. Activated sludge was used as a typical mixed culture. The coefficient of variation of quinone content was lower than 6%, and that of microbial diversity calculated from the composition of quinones was as low as 3%. Statistical analyses on the analytical precision of quinones demonstrated that the critical value of dissimilarity between two quinone profiles of activated sludge, which is used to make a judgement whether the two quinone profiles are different or not, is 0.1 for the analytical method used in this study. The values of minimum biomass required for quinone analysis to have a reliable analytical result of microbial quinones were 2 mg-dry-cell for activated sludge.

Toward the bioremediation of dioxin-polluted soil: structural and functional analyses of in situ microbial populations by quinone profiling and culture-dependent methods

In order to obtain basic information toward the bioremediation of dioxin-polluted soil, microbial communities in farmland soils polluted with high concentrations of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) were studied by quinone profiling as well as conventional microbiological methods. The concentration of PCDD/Fs in the polluted soils ranged from 36 to 4,980 pg toxicity equivalent quality (TEQ) g(-1) dry weight of soil. There was an inverse relationship between the levels of PCDD/Fs and microbial biomass as measured by direct cell counting and quinone profiling. The most abundant quinone type detected was either MK-6 or Q-10. In addition, MK-8, MK-8(H2), and MK-9(H8) were detected in significant amounts. Numerical analysis of quinone profiles showed that the heavily polluted soils (> or = 1,430 pg TEQ g(-1)) contained different community structures from lightly polluted soils (< or = 56 pg TEQ g(-1)). Cultivation of the microbial populations in the heavily polluted soils with dibenzofuran or 2-chlorodibenzofuran resulted in enrichment of Q-10-containing bacteria. When the heavily polluted soil was incubated in static bottles with autoclaved compost as an organic nutrient additive, the concentrations of PCDD/Fs in the soil were decreased by 22% after 3 months of incubation. These results indicate that dioxin pollution exerted a significant effect on microbial populations in soil in terms of quantity, quality, and activity. The in situ microbial populations in the dioxin-polluted soil were suggested to have a potential for the transformation of PCDD/Fs and oxidative degradation of the lower chlorinated ones thus produced.

Effect of pH on the reduction of nitrite in water by metallic iron

Chemical reduction is an alternative technique to remove nitrogen oxides from contaminated groundwater and closed-surface water body. Metallic iron was employed as a reductant for the reduction of nitrite in water in this study. The effect of pH on the rate and products of nitrite reduction was investigated with a fixed dosage of metallic iron powder (12 mol-Fe/mol-N, size of the powder: 80 mesh). The reduction of nitrite by metallic iron was a pseudo-zero-order reaction under the experimental conditions. The reduction rate of nitrite was increased with decreasing the pH of reaction solution, and the pseudo-zero-order reaction rate constants were 180, 130, 60, 15, 10, and 1 mM/h at pH = 2, 3, 4, 5, 6, and 7, respectively. The reduction products of nitrite were nitrogen gas and ammonium. The yields of nitrogen gas from nitrite reduction were 0.63, 0.74, 0.81, 0.87, 0.92, and 0.98 as molar ratios of nitrogen atom at pH =2, 3, 4, 5, 6, and 7, respectively. Neutral condition enhanced the formation of nitrogen gas from nitrite reduction.

beta-sheet structure formation of proteins in solid state as revealed by circular dichroism spectroscopy

Cross beta-sheet structure formation and abnormal aggregation of proteins are thought to be pathological characteristics of some neurodegenerative disorders. To investigate the novel structural transformation and aggregation, the solid-state secondary structures of some proteins and peptides associated in thin films were determined by circular dichroism spectroscopy. Insulin, lysozyme, DsbA protein, luciferase, and ovalbumin peptide fall into one group; they show no or slight structural rearrangement from solution to the solid state. Another group, including bovine serum albumin, ovalbumin, alpha-synuclein, and plasminogen activator inhibitor-1 (PAIRC) peptide, undergo structural transformation with an increase of beta-sheet structure in the solid state. The beta-sheet formation of PAIRC peptide may reflect the structural transformation of the serpin reactive center that is relevant to the inhibitor activity. The beta-sheet structure of alpha-synuclein in the solid state may correspond to the amyloid-like aggregates, which are implicated in the pathogenesis of some neurodegenerative diseases.

[High expression of rabbit sperm membrane protein rSP10 in Escherichia coli and preparation of its specific antisera]

To study the position and immunogenicity of rSP10, the rabbit rsp10 gene which did not include sequences coding for signal peptides was inserted into expression vector pET30a. An in-frame fusion protein was made such that a His6 stretch was produced at the N terminus of re-rSP10. High expression was obtained, the amount of re-rSP10 up to 67% in the total bacterial protein. The re-rSP10 was purified by DEAE chromatography and the yield of purified re-rSP10 was approximately 50 micrograms/mL of culture. Western blotting analysis of re-rSP10 with rabbit polyclonal sera raised against rabbit sperm membrane protein showed that the synthesized antigen possessed immunogenicity of rSP10. Specific antisera against re-rSP10 was induced using purified re-rSP10 as an antigen. The motility of capacitated sperms were affected but no aggregation was observed.

Analysis of material and energy flow in sewage treatment facilities in Japan

Energy consumption in sewage treatment facilities in Japan has increased due to increasing tap water consumption. To reduce the resource/energy consumption in sewage treatment facilities, measures such as the selection of optimum treatment processes and operating conditions should be considered. The objective of this study is to gather information necessary for the determination of optimum sewage treatment processes and optimum operating conditions. The energy consumption and material flow in sewage treatment facilities in Japan are analyzed using statistical data. In 1994, reuse rate of treated sewage outside the treatment facilities in Japan was 18% of the amount of domestic treated water. In this regard, reuse of water outside facilities should be encouraged. Average electric power consumption per unit volume of wastewater in sewage treatment facilities varies widely from facility to facility and closely correlates with the facility scale. For example, the smaller the facility scale, the larger the electric power consumption. Treatment volume of sewage in smaller facilities is much less than their capacity. 3.7 million t year-1 of dehydration cake is incinerated and 0.1 million t year-1 of it is converted by composting. The recycle rate of the cake was low. Developing a new sludge treatment process other than incineration is necessary.

[Genetic studies of 13 loci in Guangdong Han population by two multiplex PCR systems and its forensic application]

OBJECTIVE

The genetic studies of 13 short tandem repeats(STRs) loci in two multiplex amplification systems were carried out on Chinese Han population in Guangdong.

METHODS

DNA samples from 328 unrelated individuals were screened. The 13 loci were D3S1358, vWA, FGA, D8S1179, D21S11, D18S51, D5S818, D13S317, D7S820, D16S539, TH01, TPOX and CSF1PO. The PCR products were analyzed and genotyped by ABI 377-96 Sequencer.

RESULTS

The combined power of discrimination (DP) was 0.999999999999993 and the combined paternity of exclusion(PE) was 99.999%. These 13 loci met the Hardy-Weinberg expectations.

CONCLUSION

The two multiplex amplification systems were very useful in forensic case investigation.

Influence of gamma irradiation and storage on apheresis platelets

BACKGROUND AND PURPOSE

Gamma irradiation of platelet concentrates to prevent graft-versus-host disease may inactivate contaminated lymphocytes and subsequently inhibit the synthesis of cytokines in the apheresis platelets during storage. We investigated the influence of irradiation and storage on apheresis platelets collected with the COBE Spectra or Fenwal CS-3000 Plus systems.

METHODS

Eleven units of apheresis platelets were collected with a COBE Spectra cell separator and another 11 units with a Fenwal CS-3000 Plus system. Each unit of apheresis platelets was divided into two equal parts: one was irradiated with 3000 cGy directly after blood donation, and the other served as a control. Cell counts, platelet activation marker CD62 antigen, blood gas values, and supernatant concentrations of K+, Na+, lactate, glucose, interleukin-1 beta (IL-1 beta), IL-8, and tumor necrosis factor-alpha (TNF-alpha) were determined in paired samples on the day of collection (day 0) and after 5 days of storage (day 5).

RESULTS

No significant differences in white cell counts or TNF-alpha concentrations were noted between the irradiated and control platelets on day 0 or day 5, whereas the mean proportion of platelets expressing CD62P (22.65% vs 25%, p = 0.014) and the mean IL-1 beta (45.55 pg/mL vs 52.75 pg/mL, p = 0.004) and IL-8 concentrations (10.68 pg/mL vs 13.07 pg/mL, p = 0.015) were significantly lower in irradiated than control platelets on day 5. The 5-day storage significantly increased the mean proportion of platelets expressing CD62P (25.00% vs 15.02%, p = 0.008), mean PO2 (116.34 mm Hg vs 98.07 mm Hg, p = 0.002), and mean concentrations of K+ (3.30 mmol/L vs 3.06 mmol/L, p < 0.001), lactate (15.12 mmol/L vs 3.23 mmol/L, p < 0.001), IL-1 beta (52.75 pg/mL vs 29.73 pg/mL, p = 0.001), and IL-8 (13.07 pg/mL vs 3.62 pg/mL, p < 0.001). Five-day storage also significantly decreased white cell count (0.18 x 10(8) vs 0.74 x 10(8), p < 0.001), PCO2 (19.38 mm Hg vs 50.51 mm Hg, p < 0.001), and concentrations of HCO3- (10.36 mmol/L vs 21.34 mmol/L, p < 0.001) and glucose (193.37 mg/dL vs 309.18 mg/dL, p < 0.001). Platelet counts and concentrations of IL-1 beta, IL-8, and TNF-alpha on day 0 did not differ significantly between control apheresis platelets collected with the Fenwal CS-3000 Plus and those collected with COBE Spectra. The mean white cell count (1.29 x 10(8) vs 0.19 x 10(8), p = 0.002) and the proportion of platelets expressing CD62P (24.71% vs 7.09%, p < 0.001) on day 0, however, were significantly higher in the platelets collected with the Fenwal CS3000-Plus than in those collected with the COBE Spectra.

CONCLUSIONS

Gamma irradiation of apheresis platelets inhibits the expression of platelet CD62P and the secretion of IL-1 beta and IL-8 after 5 days' storage.

Substrate interactions in BTEX and MTBE mixtures by an MTBE-degrading isolate

Groundwater contaminant plumes from recent accidental gasoline releases often contain the fuel oxygenate MTBE (methyl tert-butyl ether) together with BTEX (benzene, toluene, ethylbenzene, o-xylene, m-xylene and p-xylene) compounds. This study evaluates substrate interactions during the aerobic biotransformation of MTBE and BTEX mixtures by a pure culture, PM1, capable of utilizing MTBE for growth. PM1 was unable to degrade ethylbenzene and two of the xylene isomers at concentrations of 20 mg/L following culture growth on MTBE. In addition, the presence of 20 mg/L of ethylbenzene or the xylenes in mixtures with MTBE completely inhibited MTBE degradation. When MTBE-grown cells of PM1 were exposed to MTBE/benzene and MTBE/toluene mixtures, MTBE degradation proceeded, while the degradation of benzene and toluene was delayed for several hours. Following this initial lag, benzene and toluene were degraded rapidly, while the rate of MTBE degradation slowed significantly. MTBE degradation did not increase to previous rates until benzene and toluene were almost entirely degraded. The lag in benzene and toluene degradation was presumably due to the induction of the enzymes necessary for BTEX degradation. Once these enzymes were induced, sequential additions of benzene or toluene were degraded rapidly, and growth on benzene and toluene was observed. The results of this study suggest that BTEX and MTBE degradation occurs primarily via two independent and inducible pathways. If subsurface microbial communities behave similarly to the culture used in this study, the observed severe inhibition of MTBE degradation by ethylbenzene and the xylenes and the partial inhibition by benzene and toluene suggest thatthe biodegradation of MTBE in subsurface environments would most likely be delayed until MTBE has migrated beyond the BTEX plume.

Characterization of microbial community in an activated sludge process treating domestic wastewater using quinone profiles

The dynamics of microbial community structure of activated sludges in a small-scale domestic wastewater treatment process were examined using a novel approach of quinone profiles. The composition and content of quinones in the activated sludges were analyzed monthly over a period of one year. More than 4 types of ubiquinones and 12 types of menaquinones were observed in the activated sludges, with the dominant quinones being ubiquinone (UQ)-8, menaquinone (MK)-7, followed by UQ-10, MK-8 and MK-6. The total quinone contents in the activated sludges varied from 0.93 to 2.68 mumol per gram of particle organic carbon. The molar ratio of ubiquinones to menaquinones (UK/MK) changed from 0.38 to 0.98, indicating that anaerobic bacteria dominated the microbial community of the activated sludges examined. The ratio of UQ/MK varied similar to that of dissolved oxygen in the bulk. The microbial diversity of the activated sludges calculated from the quinone compositions was 13.4-16.8. The diversity of menaquinones was much higher than that of ubiquinones, and increased slightly with increasing temperature. The microorganisms containing menaquinones appear to be sensitive to the change in temperature than those containing ubiquinones.

Effects of temperature on biodegradation characteristics of organic pollutants and microbial community in a solid phase aerobic bioreactor treating high strength organic wastewater

The BOD removal rate and microbial community structure in a solid phase aerobic bioreactor using polyvinyl alcohol gel particles as packing material for the treatment of high strength organic wastewater were investigated at various temperatures. The BOD removal rate in the bioreactor increased when the temperature increased from 20 degrees C to 30 degrees C, 40 degrees C, and 50 degrees C, but it decreased when the temperature increased from 50 degrees C to 60 degrees C. Higher temperature enhanced the endogenous respiration of microbes in the bioreactor. The microbial community structure in the bioreactor was analyzed with quinone profile. The experimental results showed that the microbial community structure in the bioreactor was significantly affected by temperature. The dominant quinone of the microbes inhabiting the bioreactor was ubiquinone-8 at 30 degrees C, but that at 50 degrees C and 60 degrees C was menaquinone-7. It was estimated that the thermophilic Bacillus having menaquinone-7 dominated in the bioreactor at higher temperature. The microbial diversity in the bioreactor varied with temperature.

Determination of sibship by PCR-amplified short tandem repeat analysis in Taiwan

BACKGROUND

Sibship determination for any two persons whose parents have died is one of the most fundamental issues of personal identification, second only to those of a parent-child relationship.

STUDY DESIGN AND METHODS

By automated fluorescence analysis of a PCR-amplified short tandem repeat (STR) system in conjunction with capillary electrophoresis, a panel of up to 15 polymorphic, autosomal, unlinked STR loci was used to investigate sibship index (SI) values in a cohort of 126 true sibling pairs. These SI values were then compared with those of 126 random pairs.

RESULTS

The 15-loci STR panel provides a cumulative power of exclusion of 0. 9999997. Of the 126 random pairs, 124 (98.4%) had cumulative sibship indices (CSIs) of <1.0, and none had a CSI of >3.0 (median, 0.0101; range, 0.0000003-2.5376). In contrast, 107 (85%) of the 126 sibling pairs had a CSI of >100 (median, 5,579.9853; range, 0.0747-9,406,829, 249.8461). However, five pairs (4%) of the sibling group had a CSI of <3.0. True sibship was confirmed for this particular group by additional paternity testing and mitochondrial DNA sequence analysis. Among a total of 1890 observations (15 loci x 126 pairs), two alleles per locus were shared 760 times (40.21%) (mean, 6.03 loci; range, 1-10) in the sibling group, but only 192 times (10.16%) in the random group (mean, 1.52 loci; range, 1-5) (p<0.001). No alleles were shared 696 times (36.83%) in the unrelated pairs, as compared to 176 times (9.31%) in the sibling group (p<0.001). A polarized distribution was not noted in the sharing of single alleles in either the random or the sibling group: 1002 observations (53.02%) and 954 observations (50.48%), respectively.

CONCLUSION

Highly polymorphic STR analysis can be discriminative in most sibship determinations, and the sharing of two alleles per locus is most informative in indicating sibship. Complementary mitochondrial DNA sequence analysis is mandatory in a few cases to exclude or establish true sibship when CSIs are equivocal and neither parent is available.

Adenine nucleotide N-glycosidase activity of the A-chain of cinnamomin characterized by 1H-nuclear magnetic resonance

Plant ribosome-inactivating proteins specifically cleave an N-glycosidic bond of a unique adenosine in the largest ribosomal RNA, releasing an adenine from ribosomes of different sources. Here, 1H-nuclear magnetic resonance is used to analyze the enzymatic products of the A-chain of cinnamomin, a type-II ribosome-inactivating protein (RIP) acting on the nucleotides in situ. The enzymatic activities of the RIP on nine nucleotides are compared. Cinnamomin A-chain can cleave the N-glycosidic bond and release an adenine base from adenine nucleotides except 5'-ATP; however, it cannot act on 5'-GMP, 5'-CMP, and 5'-UMP. The A-chain in the mixture of cinnamomin A- and B-chain exhibits higher activity toward adenine nucleotides than the A-chain alone does, suggesting that the B-chain can conformationally stabilize the A-chain. Intact cinnamomin also exhibits lower activity toward adenine nucleotides. However, cinnamomin B-chain and heat-denatured intact cinnamomin cannot hydrolyze all the tested nucleotides. We conclude that hydrolysis of the N-C glycosidic bond of nucleotide compounds by cinnamomin A-chain has a base preference, and the negatively charged phosphate group(s) reduces the recognition ability of the A-chain to adenine nucleotide.

Alpha-to-beta structural transformation of ovalbumin: heat and pH effects

Ovalbumin is an important member of the serpin superfamily without inhibitory activity. The heat- and pH-induced alpha-to-beta structural transformations of ovalbumin were investigated by means of circular dichroism and binding of ANS and Congo red dyes. The native ovalbumin shows a mixture of alpha-helix and beta-sheet, while both the heat and alkali treatments are able to transform the native protein into a predominance of beta-sheet secondary structure. The free energy changes during transitions to the unfolded state are 5.19 kcal/mol from the native state and 4.00 kcal/mol from the heat-treated one. The binding abilities of the heat-treated and the alkali-treated forms to ANS and Congo red suggest that the altered forms exhibit hydrophobic exposure and intermolecular interaction. The results substantiate that the altered protein forms bearing increased beta-sheet structures are prone to aggregation, which is implicated in the pathogenesis of some conformational diseases.

Study of the redox properties of metallothionein in vitro by reacting with DsbA protein

Mammalian metallothionein (MT) contains 20 cysteine residues involved in the two metal clusters without a disulfide bond. The redox reaction of the Cys thiols was proposed to be associated with the metal distribution of MT. The E. coli DsbA protein is extremely active in facilitating thiol/disulfide exchange both in vivo and in vitro. To further investigate the redox properties of MT, reaction between MT and DsbA was carried out in vitro by fluorescence detection. Equilibrium characterization indicates that the reaction is stoichiometric (1:1) under certain conditions. Kinetic study gives a rate constant of the redox reaction of 4.42 x 10(5) sec(-1) M(-1), which is 10(3)-fold larger than that of glutathione reacting with DsbA. Metal-free MT (apo-MT) shows a higher equilibrium reduction potential than MT, but exhibits an indistinguishable kinetic rate. Oxidation of MT by DsbA leads to metal release from the clusters. The characteristic fluorescence increase during reduction of DsbA may provide a sensitive probe for exploring the redox properties of some reductants of biological interest. The result also implies that oxidation of Cys thiols may influence the metal release or delivery from MT.

Acute and chronic phase platelet aggregability studies in Chinese patients after implantation of a permanent transvenous pacemaker

It has been suggested that the incidence of thromboembolic events always increases in patients after insertion of a transvenous pacemaker. Blood samples from twenty consecutive patients (fifteen males and five females) before and after pacemaker implantation was retained for platelet aggregability studies which were analyzed separately with ADP, collagen, epinephrine and arachidonic acid. The maximal amplitude of platelet aggregatory curve was detected by an aggregometer. The samples collected the day before pacemaker implantation (day 0) were used as self-control. Day 1 and day 3 after pacemaker implantation were defined as the acute phase, while day 30 was defined as the chronic phase. The maximal amplitude of platelet aggregatory curve was observed to be lowest on day 1 and then return to normal on day 3 and day 30. The results of platelet aggregability, however, showed no significant difference (P>0.05) between self-control and post-implantation samples. In conclusion, there was no significant change in platelet aggregability for either acute or chronic phases after pacemaker implantation. Antiplatelet medications may not be necessary for the prevention of thromboembolic events after the implantation of a pacemaker.

Factors affecting progenitor cell yields using three tandem leukaphereses in previously treated malignancies

BACKGROUND

Mobilized peripheral blood progenitor cells (PBPCs) have increasingly been used to replace autologous bone marrow to allow faster hematopoietic reconstitution after myeloablative therapy in various malignancies. There is a paucity of data concerning factors that affect the total yield of three tandem leukaphereses.

METHODS

Factors affecting the yield of PBPCs were analyzed in a series of 121 consecutive patients including 36 with non-Hodgkin's lymphoma, two with Hodgkin's disease, four with multiple myeloma, 44 with acute leukemia, 20 with breast cancer and 15 with other solid tumors. PBPCs were mobilized using granulocyte-colony-stimulating factor (G-CSF) alone (group I, n = 15), or after conventional-dose (group II, n = 70) or high-dose (group III, n = 36) chemotherapy followed by G-CSF. The total yield of three tandem PBPC collections for each patient was assessed by the number of mononuclear cells (MNCs), CD34+ cells and colony-forming units of granulocyte macrophages (CFU-GM). The factors evaluated included age, sex, diagnosis, history of marrow involvement, previous radiotherapy, the number of prior chemotherapy cycles and mobilization method. The two -sample t-test and logistic regression analysis were performed for univariate and multivariate analysis, respectively.

RESULTS

With univariate analysis, a diagnosis of acute leukemia, positive history of bone marrow involvement, more chemotherapy cycles and mobilization with high-dose chemotherapy adversely affected the yields of CD34+ cells. By multivariate analysis, Group II had higher yields of MNCs (p = 0.039), CFU-GM (p = 0.002) and CD34+ cells (p = 0.011) than Group III. Fewer cycles of prior chemotherapy is the common favorable factor for the yields of both CD34+ cells (p = 0.016) and CFU-GM (p = 0.017).

CONCLUSIONS

The number of prior chemotherapy cycles adversely affects progenitor cell yield. Conventional-dose chemotherapy followed by G-CSF seems to be the mobilization methods of choice for heavily pretreated cancer patients with limited bone marrow reserve. PBPCs should be harvested early, when the tumor burden is less, to avoid cumulative marrow toxicity from chemotherapy.

Polymorphisms of twelve short tandem repeat loci in a Taiwanese population and their application in parentage testing

With the advancement of techniques in molecular biology, rapid, sensitive, and reliable methods of DNA typing for parentage testing have become available. In this study, we evaluated the usefulness of multiplex polymerase chain reaction (PCR) with 12 unlinked short tandem repeat (STR) loci for paternity testing in Taiwan. The genetic informativeness of this test was then compared with that of conventional human leukocyte antigen (HLA) analysis in 167 parentage studies. The 12 STR loci alone provided a cumulative power of exclusion of up to 0.9998. Paternity was excluded in 59 (35.3%) cases, including 40 of 112 paternity trios and 19 of 55 paternity duos. In the 40 trios in which paternity was excluded, a mean of 6 (range, 3-9) incompatible STR markers were in the 19 duos in which paternity was excluded, a mean of 4 (range, 1-8) incompatible STR markers were noted. In the 72 trios in which the alleged paternity could not be excluded, the mean probabilities of paternity (PP) were 90.6863% with HLA testing alone, 99.9847% with STR analysis alone, and 99.9972% with combined HLA and STR analysis. In the 36 duos in which the alleged paternity could not be excluded, the mean PPs were 81.4768% with HLA testing alone, 99.6124% with STR analysis alone, and 99.9145% with combined HLA and STR analysis. These results suggest that STR analysis is very powerful when used alone for paternity trio testing and when combined with conventional serologic HLA typing for duo parentage testing in the Taiwan population.

The effects of helix breaking mutations in the diphtheria toxin transmembrane domain helix layers of the fusion toxin DAB389IL-2

The fusion protein toxin DAB389IL-2 is composed of the catalytic and transmembrane domains of diphtheria toxin genetically linked to human interleukin 2 (IL-2). This fusion toxin is selectively toxic for eukaryotic cells which express the high-affinity form of the IL-2 receptor and the mechanism of intoxication parallels that of native diphtheria toxin. We used site-directed mutagenesis to introduce Pro residues into each of the three helical layers of the transmembrane domain. Although each of the mutations results in the complete loss of cytotoxic activity, individual mutants were found to vary with respect to channel formation in planar lipid bilayers, binding affinity and melting temperature. We propose that each of the three helix layers plays a critical role in the productive delivery of the catalytic domain to the cell cytosol.