Hair follicle: a reliable source of recipient origin after allogeneic hematopoietic stem cell transplantation

Blood, buccal swab and hair follicles are among the most commonly used sources for forensic science, parentage testing and personal identification. A total of 29 patients who have had a sustained engraftment from 15 months to 21.5 years after allogeneic hematopoietic stem cell transplantation (HSCT) without rejection, relapse or chronic GVHD involving oral mucosa were enrolled for a chimerism study. PCR-amplified short tandem repeat analyses were conducted per patient every 3 months for at least three consecutive times. The results for blood were all donor type except one who had a mixed chimerism, 14.5 years after receiving a transplant for lymphoma. As for buccal swab, mixed chimerism ranging from 10 to 96% donor origin was noted for 28 recipients except the one who had mixed chimerism of blood and retained total recipient type. In contrast, hair follicles were 100% recipient type for the entire group. It is concluded that the hair follicle is devoid of adult stem cell plasticity and may serve as a reliable source of recipient's origin when pre-transplant DNA fingerprinting or reference DNA is not available for people who have successfully received allogeneic HSCT while in need of a personal identification.

Y-chromosome short tandem repeats analysis to complement paternal lineage study: a single institutional experience in Taiwan

BACKGROUND

Highly polymorphic autosomal short-tandem-repeat (STR) analysis can be useful in most kinship testing. Y-chromosome-specific STRs, in contrast, have been increasingly applied for the verification of equivocal paternal genetic transmissions.

STUDY DESIGN AND METHODS

A total of 338 unrelated males were first typed for the 9-loci Y-STR European minimal haplotype (minHt). Samples with haplotypes that were found at least two times were subject to further study by a commercially available 17-Y-STR multiplex set (AmpFlSTR Yfiler). A separate clinical study for 113 various kinship identifications of male genetic transmission were then conducted by a panel consisting of 18 autosomal STRs and complemented by both Y-STR multiplex sets and their respective results compared.

RESULTS

For the 338 individuals, a total of 270 haplotypes were identified after the minHt study, of which 234 were unique. Among the rest of the 104 samples, AmpFlSTR Yfiler identified 82 other unique haplotypes. Altogether, 324 different haplotypes were observed; 316 (97.5%) were unique whereas 8 were shared by two to seven times. The haplotype diversities for the minHt and the AmpFlSTR Yfiler were 99.75 and 99.96 percent, respectively, whereas the powers of discrimination (PDs) were 79.88 and 95.86 percent, respectively. Despite a lower PD for minHt, there was no discrepancy on the clinical setting for personal identification between the two Y-STR sets in an allegedly true male lineage transmission involving 66 cases with 24 father-son, 19 siblings, 9 uncle-nephew, 8 grandfather-grandson, 3 cousins, and 3 half-siblings. For 47 other cases with a false allegation of paternity, exclusion was made for all without ambiguity by either Y-STR panel.

CONCLUSION

The 9-loci minHt Y-STR set is adequate to complement conventional autosomal STRs for kinship studies where Y-lineage transmission is concerned.

Characterization of a bifunctional aminoacylase/carboxypeptidase from radioresistant bacterium Deinococcus radiodurans R1

The gene encoding a Deinococcus radiodurans R1 bifunctional aminoacylase/carboxypeptidase (DR_ACY/CP) was amplified by polymerase chain reaction and cloned into pQE-30 to generate pQE-DRAC. The cloned gene consists of an open reading frame of 1197 bp encoding a protein with a molecular mass of 42,729 Da. The predicted amino acid sequence shows high homology with those of Geobacillus kaustophilus aminoacylase, Geobacillus stearothermophilus aminoacylase, Pyrococcus horikoshii carboxypeptidase/aminoacylase and Thermoanaerobacter tengcongensis aminoacylase/carboxypeptidase. The expressed enzyme was purified from the crude extract of IPTG-induced Escherichia coli M15 (pQE-DRAC) to homogeneity by nickel-chelate chromatography. The molecular mass of the purified enzyme was determined to be 43kDa by SDS-PAGE. Maximal aminoacylase activity with N-acetyl-methionine as the substrate occurred at pH 8.0 and 40 degrees C in the sodium phosphate buffer. The aminoacylase activity was strongly inhibited by metal-chelating agents, and was largely restored by divalent cations, such as Co(2+), Mn(2+) and Ni(2+). The purified enzyme had broad specificity toward N-acetylated L-amino acids as well as N-CBZ-peptides. Carboxypeptidase activity of DR_ACY/CP to N-CBZ-Gly-Ala exhibited K(m) and k(cat) values of 4.3mM and 28s(-1), respectively. The enzyme also had activity toward the cell wall-related substrates, D-Ala-Gly, D-Ala-Gly-Gly and L-Orn-L-Ala.

Overexpression of a recombinant gamma-glutamyltranspeptidase from Escherichia coli Novablue

A truncated Escherichia coli Novablue gamma-glutamyltranspeptidase (EcGGT) gene, lacking the first 48-bp coding sequence for part of the signal sequence, was amplified by polymerase chain reaction (PCR) and cloned into expression vector pQE-30 to generate pQE-EcGGT. The maximum production of His6-tagged enzyme by E. coli M15 (pQE-EcGGT) was achieved with 0.1 mM IPTG induction for 12 h at 20 degrees C. The overexpressed enzyme was purified to homogeneity by nickel-chelate chromatography to a specific transpeptidase activity of 4.25 U/mg protein and a final yield of 83%. The molecular masses of the subunits of the purified enzyme were determined to be 41 and 21 kDa respectively by SDS-PAGE, indicating the precursor EcGGT still undergoes the post-translational processing even in the truncation of signal sequence. His6-tagged EcGGT migrated relative to the molecular mass of approximately 120 kDa and its heterodimeric structure was confirmed by a native-PAGE gel.

Expression Optimization and Biochemical Characterization of a Recombinant γ-Glutamyltranspeptidase from Escherichia coli Novablue

A truncated Escherichia coli Novablue gamma-glutamyltranspeptidase (EcGGT) gene lacking the first 48-bp coding sequence for part of the signal sequence was amplified by polymerase chain reaction and cloned into expression vector pQE-30 to generate pQE-EcGGT. The maximum production of His(6)-tagged enzyme by E. coli M15 (pQE-EcGGT) was achieved with 0.1 mM IPTG induction for 12 h at 20 degrees C. The overexpressed enzyme was purified to homogeneity by nickel-chelate chromatography to a specific transpeptidase activity of 4.25 U/mg protein and a final yield of 83%. The molecular masses of the subunits of the purified enzyme were estimated to be 41 and 21 kDa respectively by SDS-PAGE, indicating EcGGT still undergoes the post-translational cleavage even in the truncation of signal sequence. The optimum temperature and pH for the recombinant enzyme were 40 degrees C and 9, respectively. The apparent K (m) and V (max) values for gamma-glutamyl-p-nitroanilide as gamma-glutamyl donor in the transpeptidation reaction were 37.9 microM and 53.7 x 10(-3) mM min(-1), respectively. The synthesis of L -theanine was performed in a reaction mixture containing 10 mM L -Gln, 40 mM ethylamine, and 1.04 U His(6)-tagged EcGGT/ml, pH 10, and a conversion rate of 45% was obtained.

A novel mitochondrial DNA missense mutation at G3421A in a family with maternally inherited diabetes and deafness

OBJECTIVE

Mutations in mtDNA are thought to be responsible for the pathogenesis of maternally inherited diabetes. Here, we report a family with maternally inherited diabetes and deafness whose members did not harbour the mtDNA A3243G mutation, the most frequent point mutation in mitochondrial diabetic patients. This study aimed to investigate a possible other mtDNA mutation and its prevalence in type 2 diabetic patients.

METHODS

Height, body weight, waistline, and hip circumference were measured and serum biochemical marks determined in all members of the family. In addition, a 75 g oral glucose tolerance test and electric listening test were conducted in these members. Genomic DNA was prepared from peripheral leukocytes. Direct sequencing of PCR products was used to detect the mtDNA mutation in this family. The prevalence of mtDNA G3421A nucleotide substitutions was investigated by restriction fragment length polymorphism analysis in 1350 unrelated type 2 diabetic patients recruited by random cluster sampling from the central city area of Shanghai, China.

RESULTS

(1) A new missense homoplasmic mutation of mtDNA G3421A was found in a maternally inherited diabetic family and existed neither in 1350 unrelated type 2 diabetic patients nor in 50 non-diabetic individuals. (2) The mode of mutation and diabetes transmission was typical maternal inheritance in this family. (3) All diabetic family members were found to have an onset at 35-42 years of age, accompanied by deafness of varying degrees.

CONCLUSION

mtDNA G3421A (Val39Ile) found in a family with maternally inherited diabetes and deafness is a novel missense mutation. Whether this is a diabetogenic mutation and its effect on mitochondrial function needs to be further studied.

Screening of Compactin-Resistant Microorganisms Capable of Converting Compactin to Pravastatin

A simple method of using compactin for effective screening of microbial strains with high hydroxylation activity at the 6beta position of compactin was developed. Agar plates containing different carbon sources and 500 microg compactin mL(-1) were used to screen the microorganisms that can convert compactin to pravastatin. About 100 compactin-resistant strains were isolated from the Basal agar containing 7% (w/v) mannitol as a carbon source, in which two bacteria, Pseudomocardia autotrophica BCRC 12444 and Streptomyces griseolus BCRC 13677, capable of converting compactin to pravastatin with the yield of 20 and 32% (w/w), respectively, were found. High-performance liquid chromatography using C-18 column and two sequential mobile phases, 30% and 50% (v/v) acetonitrile, was also established to simultaneously determine the concentration of compactin and pravastatin in the culture broth. As such, about 2% of target microorganisms could be obtained from the screening program.

Novel polymorphisms in exons 6 and 7 of A/B alleles detected by polymerase chain reaction-single strand conformation polymorphism

BACKGROUND AND OBJECTIVES

The ABO blood group system is the most important blood group system in transfusion medicine. In addition to the major A, B and O alleles, many rare alleles have been defined. Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and analysis by PCR sequence specific primers (SSP) are commonly conducted for genotyping but have the limitation of being unable to detect unknown substitution(s) in amplified DNA fragments, whereas PCR-single strand conformation polymorphism (SSCP) can be used for both.

MATERIALS AND METHODS

Three-hundred unrelated blood donors of the AB phenotype were enrolled. Four pairs of primers were designed to constitute two sets of multiplex PCRs: this amplifies four fragments spanning the entire exon 6 and its immediate flanking regions, nucleotides 432-1065, as well as the 3' untranslated region of exon 7 of the ABO gene. The SSCP electrophoresis was carried out on a 12.5% polyacrylamide gel in a GenePhor electrophoresis unit. For those with unexpected banding patterns, SSCP analyses were performed in duplicate and samples were cloned and sequenced for exons 6 and 7.

RESULTS

Seven samples were noted to have six variant alleles, of which five have not been previously reported in the literature. Of these five novel variants, four were derived from the B allele, while the other derived from the A allele.

CONCLUSIONS

By using PCR-SSCP, five novel A/B alleles were found.

Antitumor effect of antisense ODC adenovirus on human prostate cancer cells

Ornithine decarboxylase (ODC), the first enzyme of polyamine biosynthesis, was found to increase in cancer cells, especially prostate cancers. Some chemotherapeutic agents aimed to decrease ODC expression showed inhibitory effects on cancer cells. In this study, we examined the effect of adenoviral-transduced antisense ODC on prostate cancer cells. An adenovirus carrying antisense ODC (rAd-ODC/Ex3as) was infected to prostate cancer cells PC-3 and LNCap. Expression of ODC and concentration of polyamines in cells were determined by Western blotting and HPLC. MTT (3-(4,5-methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide) assay was used to analyze the effect on cell growth. Cell cycle was evaluated by FCM and cellular invasion by Matrigel invasion assay. A nude mouse xenograft model was used to examine tumorigenicity. Expression of ODC in PC-3 and LNCap cells were reduced to 45 and 59%, and three polyamines were also decreased by the rAd-ODC/Ex3as treatment. Consequently, cell growth was substantially inhibited and cell cycle arrested at G1 phase. Matrigel invasion assay showed relatively low invasion. Marked suppression of tumor formation was observed in the xenograft model. This study suggests that rAd-ODC/Ex3as has the antitumor effect on the human prostate cancer cells.

Development of a novel solid phase extraction method for the analysis of bacterial quinones in activated sludge with a higher reliability

A novel analytical method for analysis of microbial quinones in activated sludge sample was developed with improved reliability compared to the conventional method. The operating conditions for the extraction of quinones from activated sludge sample with a methanol-chloroform mixture and hexane were optimized. A solid phase extraction method using the Sep-Pak Plus Silica, a small column packed with silica gel, was employed for the purification and separation of quinones instead of column chromatography and thin layer column chromatography used in the conventional method. The analytical operation was simplified and the analytical time was shortened by a half or two-thirds of that required for the conventional method. The recoveries of quinones were markedly increased from 30-60% with the conventional method to as high as 90-101% with the improved method, demonstrating that the reliability of the analytical results of the improved method is significantly higher than that of the conventional method. The quinone content value obtained using the improved method was twice as high as that obtained using the conventional method for the same activated sludge sample, but the quinone profiles expressed as the mole fraction of each quinone type were the same for each method.

Phylogenetic Analysis and Biochemical Characterization of a Thermostable Dihydropyrimidinase from Alkaliphilic Bacillus sp. TS-23

Two degenerate primers established from the alignment of highly conserved amino acid sequences of bacterial dihydropyrimidinases (DHPs) were used to amplify a 330-bp gene fragment from the genomic DNA of Bacillus sp. TS-23 and the amplified DNA was successfully used as a probe to clone a dhp gene from the strain. The open reading frame of the gene consisted of 1422 bp and was deduced to contain 472 amino acids with a molecular mass of 52 kDa. The deduced amino acid sequence exhibited greater than 45% identity with that of prokaryotic D-hydantoinases and eukaryotic DHPs. Phylogenetic analysis showed that Bacillus sp. TS-23 DHP is grouped together with Bacillus stearothermophilus D-hydantoinase and related to dihydroorotases and allantoinases from various organisms. His6-tagged DHP was over-expressed in Escherichia coli and purified by immobilized metal affinity chromatography to a specific activity of 3.46 U mg(-1) protein. The optimal pH and temperature for the purified enzyme were 8.0 and 60 degrees C, respectively. The half-life of His6-tagged DHP was 25 days at 50 degrees C. The enzyme activity was stimulated by Co2+ and Mn2+ ions. His6-tagged DHP was most active toward dihydrouracil followed by hydantoin derivatives. The catalytic efficiencies (kcat/Km) of the enzyme for dihydrouracil and hydantoin were 2.58 and 0.61 s(-1) mM(-1), respectively.

A novel cis-AB allele derived from a unique 796C>A mutation in exon 7 of ABO gene

BACKGROUND

The cis-AB phenotype is very rare, and only three genotypes that correspond to specific ABO allele changes have been reported. Cis-AB01 involves the A102 allele with a nonsynonymous substitution G803C in exon 7, whereas cis-AB02 and cis-AB03 involve different nonsynonymous substitutions A796C and C700T, respectively, on the B101 allele background. The nucleotide substitutions give rise to a change of the respective glycosyltransferase, resulting in varying bifunctional AB transferase activities.

STUDY DESIGN AND METHODS

Two cis-AB phenotypes were identified in a Taiwanese C. family and two unrelated individuals, respectively. Serologic studies, molecular cloning, and sequencing of exon 6 and exon 7 were carried out to determine their respective phenotypic characteristics and cis-AB alleles. A cohort of 300 AB-phenotype, healthy random individuals served as controls.

RESULTS

A novel cis-AB allele is uncovered out of the three family members, of which a 796C>A substitution occurs predicting an amino acid change at residue 266 of leucine to methionine on the background of A102 allele. It is serologically like cis-AB03, an A2B phenotype, but molecularly different. Both of the two unrelated individuals are of cis-AB01 allele, and all of the 300 AB blood group controls are excluded cis-AB phenotype.

CONCLUSION

The C. family described carries a novel cis-AB allele that differs molecularly from all previously reported cis-AB alleles.

Structural genomics efforts at the Chinese Academy of Sciences and Peking University

Structural genomics efforts at the Chinese Academy of Sciences and Peking University are reported in this article. The major targets for the structural genomics project are targeted proteins expressed in human hematopoietic stem/progenitor cells, proteins related to blood diseases and other human proteins. Up to now 328 target genes have been constructed in expression vectors. Among them, more than 50% genes have been expressed in Escherichia coli, approximately 25% of the resulting proteins are soluble, and 35 proteins have been purified. Crystallization, data collection and structure determination are continuing. Experiences accumulated during this initial stage are useful for designing and applying high-throughput approaches in structural genomics.

QSAR-based toxicity classification and prediction for single and mixed aromatic compounds

Quantitative structure-activity relationships (QSARs) based on the octanol/water partition coefficient were employed to predict acute toxicities of 36 substituted aromatic compounds and their mixtures. In this study, the model developed by Verhaar et al. was modified and used to calculate octano/water partition coefficients of chemical mixtures. To validate the model, acute toxicities of these chemicals were measured to Vibrio fischeri in terms of EC50. The results indicated that the obtained QSAR models could be used to predict toxicities of samples consi sting of these substituted aromatic compounds, individually or in combinations. The obtained equations were proved to be robust enough by using the leave-one-out test method. By classifying these chemicals into two groups, polar and non-polar, the toxicities of chemical mixtures within each group can be predicted accurately from their calculated partition coefficients.

Site-Directed Mutagenesis of the Conserved Threonine, Tryptophan, and Lysine Residues in the Starch-Binding Domain of Bacillus sp. Strain TS-23 a-Amylase

The C-terminal domain of Bacillus sp. strain TS-23 alpha-amylase (BLA) has been known to be involved in the raw starch-binding activity of the enzyme. Sequence comparison revealed that Thr-527, Trp-545, Trp-561, Lys-576, and Trp-588 in this domain are highly conserved in the aligned enzymes. To understand structure-function relationships in the starch-binding domain of BLA, site-directed mutagenesis was conducted to replace these residues with leucine or isoleucine. The overexpressed enzymes have been purified by nickel-chelate chromatography, and the molecular mass of the purified proteins was approximately 64.5 kDa. Starch-binding assay showed that the binding activities of the single-mutated enzymes were significantly reduced, while the combinational mutations did not lead to a complete loss of the activity.

A thermostable leucine aminopeptidase from Bacillus kaustophilus CCRC 11223

Two degenerate primers established from the consensus sequences of bacterial leucine aminopeptidases (LAP) were used to amplify a 360-bp gene fragment from the chromosomal DNA of thermophilic Bacillus kaustophilus CCRC 11223 and the amplified fragment was successfully used as a probe to clone a leucine aminopeptidase ( lap) gene from a genomic library of the strain. The gene consists of an open reading frame (ORF) of 1,494 bp and encodes a protein of 497 amino acid residues with a calculated molecular mass of 53.7 kDa. The complete amino acid sequence of the cloned enzyme showed greater than 30% identity with prokaryotic and eukaryotic LAPs. Phylogenetic analysis showed that B. kaustophilus LAP is closely related to the enzyme from Bacillus subtilis and is grouped with the M17 family. His6-tagged LAP was generated in Escherichia coli by cloning the coding region into pQE-30 and the recombinant enzyme was purified by nickel-chelate chromatography. The pH and temperature optima for the purified enzyme were 8 and 65 degrees C, respectively, and 50% of its activity remained after incubation at 60 degrees C for 32 min. The enzyme preferentially hydrolyzed L-leucine- p-nitroanilide ( L-Leu- p-NA) followed by Cys derivative.

Oxidative treatment characteristics of biotreated textile-dyeing wastewater and chemical agents used in a textile-dyeing process by advanced oxidation process

The oxidative treatment characteristics of biotreated textile-dyeing wastewater and typical chemicals such as desizing, scouring, dispersing and swelling agents used in the textile-dyeing process by advanced oxidation process were experimentally studied. The refractory organic matters remained in the effluent of biological treatment process without degradation may be suitable for the improvement of biodegradability and mineralized to CO2 by combined ozonation with and without hydrogen peroxide. On the other hand, the refractory chemicals contained in the scouring agent A and swelling agent may not be mineralized and their biodegradability may not be improved by ozonation. However, the BOD/DOC ratio of scouring agent B increased from 0.3 to 0.45 after ozonation. Based on the results described above, advanced treatment process involving the ozonation without and with the addition of hydrogen peroxide, followed by biological treatment was proposed for the treatment of refractory wastewater discharged from the textile-dyeing process.

Molecular characterization of a family of tandemly repeated DNA sequences, TR-1, in heterochromatic knobs of maize and its relatives

Two families of tandem repeats, 180-bp and TR-1, have been found in the knobs of maize. In this study, we isolated 59 clones belonging to the TR-1 family from maize and teosinte. Southern hybridization and sequence analysis revealed that members of this family are composed of three basic sequences, A (67 bp); B (184 bp) or its variants B' (184 bp), 2/3B (115 bp), 2/3B' (115 bp); and C (108 bp), which are arranged in various combinations to produce repeat units that are multiples of approximately 180 bp. The molecular structure of TR-1 elements suggests that: (1) the B component may evolve from the 180-bp knob repeat as a result of mutations during evolution; (2) B' may originate from B through lateral amplification accompanied by base-pair changes; (3) C plus A may be a single sequence that is added to B and B', probably via nonhomologous recombination; and (4) 69 bp at the 3' end of B or B', and the entire sequence of C can be removed from the elements by an unknown mechanism. Sequence comparisons showed partial homologies between TR-1 elements and two centromeric sequences (B repeats) of the supernumerary B chromosome. This result, together with the finding of other investigators that the B repeat is also fragmentarily homologous to the 180-bp repeat, suggests that the B repeat is derived from knob repeats in A chromosomes, which subsequently become structurally modified. Fluorescence in situ hybridization localized the B repeat to the B centromere and the 180-bp and TR-1 repeats to the proximal heterochromatin knob on the B chromosome.

QSPR-based prediction of adsorption of halogenated aromatics on yellow-brown soil

Halogenated aromatic compounds exist widely in soil and aqueous environment. The study of their transport and distribution is quite important for pollution control and risk assessment. In the present work the adsorption coefficients of 28 halogenated benzenes, anilines and phenols on yellow-brown soil were measured with batch equilibrium method, and a prediction model was developed through the quantitative structure-property relationship (QSPR) technique. Then the obtained model was tested with Monte Carlo simulation and Jacknife methods. The results indicated that it was robust enough to estimate soil adsorption behaviors for the tested compounds. Based on the obtained model it could be deduced that the adsorption of halogenated aromatics on yellow-brown soil was not a simple partitioning process but involved complicated interactions.

Characterization and phylogenetic analysis of a thermostable N-carbamoyl- l-amino acid amidohydrolase from Bacillus kaustophilus CCRC11223

A thermostable N-carbamoyl- l-amino acid amidohydrolase ( l-N-carbamoylase) gene composed of an 1,230-bp ORF encoding a 44.3-kDa protein was cloned from the thermophile Bacillus kaustophilus CCRC11223. This l-N-carbamoylase contained six cysteine residues that form three disulfide bridges. The purified l-N-carbamoylase was stringently l-specific and exhibited high activity in the hydrolysis of N-carbamoyl- l-homophenylalanine. N-carbamoyl derivatives of beta-alanine, beta-aminoisobutyric acids, l-tryptophan, and d-specific amino acids were not recognized as substrates. The l-N-carbamoylase required the divalent metal ions Mn(2+), Co(2+), and Ni(2+) for increasing activity. The pH and temperature optima of the enzyme were pH 7.4 and 70 degrees C, respectively. This enzyme was completely thermostable at 50 degrees C for 36 days in the presence of d- and/or l-specific substrates. Phylogenetic analysis of the available amino acid sequences of N-carbamoyl and N-acyl amino acid amidohydrolases from the three main kingdoms of life showed that they can be divided into four distinct families. The B. kaustophilus enzyme could be classified into the family of l-N-carbamoylases and some beta-ureidopropionases, but did not hydrolyze beta-ureidopropionates.

Replacement of methionine 208 in a truncated Bacillus sp. TS-23 alpha-amylase with oxidation-resistant leucine enhances its resistance to hydrogen peroxide

The methionine residues at positions 17, 104, 208, 214, 292, 315, 324, and 446 in the primary amino acid sequence of a truncated Bacillus sp. TS-23 alpha-amylase (His(6)-tagged BLADeltaNC) was changed to oxidative-resistant leucine by site-directed mutagenesis. The mutant enzymes with an apparent molecular mass of approximately 54 kDa were overexpressed in recombinant Escherichia coli. The specific activity for Met315Leu and Met446Leu was decreased by more than 76%, while Met17Leu, Met104Leu, Met208Leu, Met214Leu, Met292Leu, and Met324Leu showed 247, 128, 37, 260, 232, and 241%, respectively, higher activity than the wild-type enzyme. In comparison with wild-type enzyme, a lower K(m) value was observed for all mutant enzymes. The 3.2- and 4.5-fold increases in the catalytic efficiency (k(cat)/K(m)) for Met208Leu and Met324Leu, respectively, were partly contributed by a 68% and 38% decrease in K(m) values. Wild-type enzyme was sensitive to chemical oxidation, but Met208Leu was stable even in the presence of 500 mM H(2)O(2). Except for Met214Leu, which was quite sensitive to H(2)O(2), the other mutants showed a profile of oxidative inactivation similar to that of the wild-type enzyme. These observations indicate that the oxidative stability of His(6)-tagged BLADeltaNC can be improved by replacement of the critical methionine residue with leucine.

HLA-DR typing by polymerase chain reaction amplification with sequence-specific primers in paternity disputes

BACKGROUND

HLA-DR typing was generally performed by serology before. HLA-DRB1 typing can be achieved by polymerase chain reaction amplification with sequence specific primers (PCR-SSP).

METHODS

In this study, primers for "low-resolution" HLA-DR typing by PCR-SSP were synthesized upon our request by a company in Taiwan. Twenty-eight DNA samples from international standardized DNA Reference Panel and 20 DNA samples with known serological typing were used as control. We conducted HLA-DR PCR-SSP typing on 18 samples from 6 true paternity trios, 16 samples from 8 true duos, 27 from 9 false trios, and 8 from 4 false duos. These DNAs from disputed paternity families had been previously tested for the parentage using polymerase chain reaction (PCR)-amplified short tandem repeat (STR) analysis.

RESULTS

No false positive nor false negative results were obtained in typing 28 positive control DNA samples from international standardized DNA Reference Panel for HLA Class II. Among the 20 DNA samples typed by microlymphocytotoxicity technique, the discordant typing results between HLA-DR PCR-SSP typing and serological typing were found in 3 (15%). In the family of true paternity, HLA-DR typing could not exclude any of alleged fathers and the pattern of inheritance was consistent with autosomal codominant. By HLA-DR typing alone, paternity in 2 alleged fathers out of 9 false trios and 2 alleged fathers out of 4 false duos could not be excluded.

CONCLUSIONS

Precise HLA-DR typing can be achieved by PCR-SSP analysis. Economic considerations preclude HLA-DR typing in routine parentage tests where STR typing is performed first.