Crystal structure of an RNA duplex r(gugucgcac)(2) with uridine bulges

The crystal structure of a nonamer RNA duplex with a uridine bulge in each strand, r(gugucgcac)(2), was determined at 1.4 A resolution. The structure was solved by multiple anomalous diffraction phasing method using a three-wavelength data set collected at the Advanced Protein Source and refined to a final R(work)/R(free) of 21.2 %/23.4 % with 33,271 independent reflections (Friedel pairs unmerged). The RNA duplex crystallized in the tetragonal space group P4(1)22 with two independent molecules in the asymmetric unit. The unit cell dimensions are a=b=47.18 A and c=80.04 A. The helical region of the nonamer adopts the A-form conformation. The uridine bulges assume similar conformations, with uracils flipping out and protruding into the minor groove. The presence of the bulge induces very large twist angles (approximately +50 degrees) between the base-pairs flanking the bulges while causing profound kinks in the helix axis at the bulges. This severe twist and the large kink in turn produces a very narrow major groove at the middle of the molecule. The ribose sugars of the guanosines before the bulges adopt the C2'-endo conformation while the rest, including the bulges, are in the C3'-endo conformation. The intrastrand phosphate-phosphate (P-P) distance of the phosphate groups flanking the bulges (approximately 4.4 A) are significantly shorter than the average P-P distance in the duplex (6.0 A). This short distance between the two phosphate groups brings the non-bridging oxygen atoms close to each other where a calcium ion is bound to each strand. The calcium ions in molecule 1 are well defined while the calcium ions in molecule 2 are disordered.

Polymorphic markers in the SRD5A2 gene and prostate cancer risk: a population-based case-control study

It has been suggested that the activity of the steroid 5alpha-reductase type II enzyme (encoded by the SRD5A2 gene) may be associated with prostate cancer risk and that population differences in this enzyme's activity may account for part of the substantial racial/ethnic disparity in prostate cancer risk. To provide etiological clues, we evaluated the relationships of four polymorphic markers in the SRD5A2 gene, specifically, A49T (a substitution of threonine for alanine at codon 49), V89L (a substitution of leucine for valine at codon 89), R227Q (a substitution of glutamine for arginine at codon 227), and a (TA)n dinucleotide repeat, with prostate cancer risk in a population-based case-control study in China, a population with the lowest reported prostate cancer incidence rate in the world. Genotypes of these four markers were determined from genomic DNA of 191 incident cases of prostate cancer and 304 healthy controls using PCR-based assays, and serum androgen levels were measured in relation to these genotypes. All study subjects had the wild-type AA genotype of the A49T marker, and 99% had the RR genotype of the R227Q marker. For the V89L marker, prevalences of the LL, VV, and VL genotypes among controls were 35%, 21%, and 45%, respectively. Compared with men with the VV genotype, those with the LL genotype had a statistically nonsignificant 12% reduced risk (odds ratio = 0.88, 95% confidence interval, 0.53-1.47). In addition, men with the LL genotype had significantly higher serum levels of testosterone and significantly lower serum levels of 5alpha-androstane-3alpha,17beta-diol glucuronide than men with other genotypes. Men heterozygous for the (TA)0 allele of the (TA)n marker had a modest, statistically nonsignificant risk reduction (odds ratio = 0.67; 95% confidence interval, 0.39-1.12) compared with men homozygous for the (TA)0 allele, along with significantly higher serum dihydrotestosterone levels. The observed V89L genotype prevalences and the association between V89L genotypes and serum androgen levels support the hypothesis that genotypes associated with lower levels of 5alpha-reductase activity are more common in low-risk populations. Although we found no statistically significant associations of these SRD5A2 polymorphisms with prostate cancer risk, a small effect of these markers cannot be ruled out because of the rarity of certain marker genotypes. Larger studies are needed to further clarify the role of these markers and to elucidate whether genetic diversity of the SRD5A2 gene, alone or in combination with other susceptibility genes, can help explain the large racial/ethnic differences in prostate cancer risk.

Crystal structures of two forms of a 14-mer RNA/DNA chimer duplex with double UU bulges: a novel intramolecular U*(A x U) base triple

The RNA/DNA 14-mer, (gguauuucgguaCc)2 with consecutive uridine bulges (underlined) on each strand has been determined in two crystal forms, spermine bound (Sp-form) and spermine free (Sp-free). The former was solved by the MAD method with three-wavelength data collected at Brookhaven National Laboratory (BNL); the later isomorphous structure was solved by the molecular replacement method using data collected on our Raxis IIc imaging plate system. The two crystal forms belong to the space group C2 with one molecule of double-stranded 14 mer in the asymmetric unit. The Sp-form has cell constants, a = 60.06, b = 29.10, c = 52.57 A, beta = 120.79 degrees and was refined to 1.7 A resolution with a final Rwork/Rfree of 19.8%/22.7% using 8,549 independent reflections. The Sp-free structure has cell constants, a = 60.06, b = 29.58, c = 52.50 A, beta = 120.85 degrees and was refined to 1.8 A with a final Rwork/ Rfree of 20.8%/23.2% using 6,285 unique reflections. The two structures are identical, except that the Sp-form has a spermine bound in the major groove, parallel to the RNA helical axis. One of the uridine bulges forms a novel intramolecular U*(A x U) base triple. The helices are in the C3'-endo conformation (A-form), but the bulges adopt the C2'-endo sugar pucker. Furthermore, the bulges induce a kink (30 degrees) in the helix axis and a very large twist (55 degrees) between the base pairs flanking the bulges. The Sp-form has one Mg2+ ion whereas the Sp-free form has two Mg2+ ions.

[The paraoxonase Gln-Arg192 polymorphism in patients with coronary heart disease in Chinese population]

OBJECTIVE

To investigate the 192 Gln-Arg polymorphism of paraoxonase (PON) gene and its relationship with serum lipids levels in patients with coronary heart disease in Chinese population.

METHODS

The genotype and allele frequency of paraoxonase gene 192 Gln-Arg polymorphism was assayed by polymerase chain reaction (PCR)-restriction fragment length polymorphism (RFLP). Serum lipids were measured by enzymatic kits in 118 CHD patients and 128 healthy subjects whose fasting serum TG levels were < 1.82 mmol/L and TC levels < 6.2 mmol/L from a population of Chinese Han nationality in Chengdu area.

RESULTS

Both in CHD group and control group, the QR genotype of PON gene was the major one, and its frequencies were 0.578 and 0.525 respectively. No differences were found in PON gene Gln-Arg polymophism in the CHD group when compared with the control group. The frequency of R allele of PON gene in Chinese was significant higher than that in European and American Caucasians (0.51 vs. 0.26-0.31, P < 0.01) and Indian (0.51 vs. 0.17, P < 0.01), and significantly lower than that in Japanese (0.51 vs. 0.65, P < 0.01).

CONCLUSION

These results suggested that the Gln-Arg192 polymorphism of the PON1 gene was not associated with coronary heart disease in Chinese population.

Monte Carlo based treatment planning for modulated electron beam radiation therapy

A Monte Carlo based treatment planning system for modulated electron radiation therapy (MERT) is presented. This new variation of intensity modulated radiation therapy (IMRT) utilizes an electron multileaf collimator (eMLC) to deliver non-uniform intensity maps at several electron energies. In this way, conformal dose distributions are delivered to irregular targets located a few centimetres below the surface while sparing deeper-lying normal anatomy. Planning for MERT begins with Monte Carlo generation of electron beamlets. Electrons are transported with proper in-air scattering and the dose is tallied in the phantom for each beamlet. An optimized beamlet plan may be calculated using inverse-planning methods. Step-and-shoot leaf sequences are generated for the intensity maps and dose distributions recalculated using Monte Carlo simulations. Here, scatter and leakage from the leaves are properly accounted for by transporting electrons through the eMLC geometry. The weights for the segments of the plan are re-optimized with the leaf positions fixed and bremsstrahlung leakage and electron scatter doses included. This optimization gives the final optimized plan. It is shown that a significant portion of the calculation time is spent transporting particles in the leaves. However, this is necessary since optimizing segment weights based on a model in which leaf transport is ignored results in an improperly optimized plan with overdosing of target and critical structures. A method of rapidly calculating the bremsstrahlung contribution is presented and shown to be an efficient solution to this problem. A homogeneous model target and a 2D breast plan are presented. The potential use of this tool in clinical planning is discussed.

Characterization of microsomal diacylglycerol acyltransferase activity from bovine adipose and muscle tissue

The activity of the triacylglycerol bioassembly enzyme, diacylglycerol acyltransferase (DGAT), was characterized in microsomal fractions prepared from bovine subcutaneous (SC) adipose, intramuscular (IM) adipose, and muscle (pars costalis diaphragmatis) tissue. The activity of DGAT was generally higher from SC adipose tissue than from IM adipose or muscle tissue. The characteristics of DGAT activity from the three bovine tissues resembled the activity characteristics observed in previous studies from various other organisms and tissues; the pH optimum was near neutrality, the activity was almost completely inhibited by pre-incubation with N-ethylmaleimide (NEM), and the enzyme accepted a broad range of acyl-CoAs and sn-1,2-diacylglycerols. In some aspects, the SC adipose tissue DGAT activity was different from the DGAT activity from the other two tissues. The SC adipose tissue DGAT activity was not as susceptible to inhibition by NEM as the enzymes from the two other tissue sources, and it exhibited increased specificity for substrates containing oleoyl moieties. The differences in DGAT properties between the three bovine tissues may account to some extent for the differences in the relative fatty acid composition and the positional distribution of fatty acids in triacylglycerol between bovine tissues. The observed differences in enzymatic properties also support recent biochemical and molecular genetic observations that imply the existence of multiple DGAT genes and/or isoforms.

Prostate cancer risk and serum levels of insulin and leptin: a population-based study

BACKGROUND

In a previous study of Chinese men, we found that men with a higher waist-to-hip ratio (WHR) have a higher prostate cancer risk. Because leptin and insulin are related to body fat distribution, we examined whether leptin and insulin were associated with prostate cancer risk.

METHODS

Blood samples were collected from 128 case patients with incident prostate cancer and from 306 healthy control subjects randomly selected from residents of Shanghai, CHINA: Epidemiologic information and anthropometric measurements were collected in personal interviews. Serum leptin, insulin, and sex hormone levels were measured by radioimmunoassay, and insulin-like growth factor-I (IGF-I) was measured by enzyme-linked immunosorbent assay. Multiple logistic regression analyses were used to estimate odds ratios for prostate cancer in relation to serum insulin and leptin levels. All statistical tests were two-sided.

RESULTS

After adjustment for body mass index, WHR, IGF-I, and sex hormone levels, higher serum insulin levels were associated with a statistically significantly elevated risk of prostate cancer (P<.001). Men in the highest tertile of insulin levels had a 2.56-fold (95% confidence interval [CI] = 1.38 to 4.75) risk of prostate cancer compared with men in the lowest tertile. Regardless of the tertile level of WHR, higher serum insulin levels were associated with an increased risk of prostate cancer: Men in the highest tertiles of WHR (>0.900) and insulin (>8.83 microU/mL) had 8.55 times (95% CI = 2.80 to 26.10) the prostate cancer risk of men in the lowest tertiles of both, and those in the lowest tertile of WHR (<0.873) and highest tertile of insulin had 4.30 times (95% CI = 1.17 to 15.70) the risk. By contrast, the association between leptin levels and prostate cancer risk was not statistically significant.

CONCLUSION

Our results suggest that serum insulin levels may influence the risk of prostate cancer in Chinese men. Further research, especially prospective studies, is needed to confirm these findings in high-risk populations and to clarify the underlying mechanisms involved.

Vitamin D receptor gene polymorphisms, insulin-like growth factors, and prostate cancer risk: a population-based case-control study in China

Operating through the vitamin D receptor (VDR), vitamin D inhibits prostate cancer growth and increases insulin-like growth factor binding protein (IGFBP) expression, suggesting that the vitamin D and insulin-like growth factor (IGF) regulatory systems may operate together to affect prostate cancer. Among 191 newly diagnosed prostate cancer cases and 304 randomly selected population controls in Shanghai, China, we found no significant association between the BsmI or FokI VDR gene polymorphisms and prostate cancer risk. However, we found that among men with the ff FokI genotype, those in the highest tertile of plasma IGFBP-3 had a decreased risk versus those in the lowest tertile (odds ratio, 0.14; 95% confidence interval, 0.04-0.56; P(trend) < 0.01), whereas among men with the FF and Ff genotypes, IGFBP-3 was not associated with risk. Similarly, IGFBP-1 was inversely associated with prostate cancer risk only among men with the ff FokI genotype (odds ratio, 0.25; 95% confidence interval, 0.07-0.85; P(trend) = 0.02). No such FokI genotype-specific effects were observed for IGF-I or IGF-II. Our findings in a low-risk population suggest that the IGF and vitamin D regulatory systems may interact to affect prostate cancer risk. Larger studies are needed to confirm these findings and clarify the underlying mechanisms.

[Antigen presentation of eosinophils in mice]

OBJECTIVE

To explore whether or not eosinophils can present antigen to T lymphocytes in vivo, and to further elucidate the process and characteristics of antigen-presentation by eosinophils in vivo.

METHODS

BALB/c mice were sensitized and challenged by ovalbumin to recruit eosinophil infiltration into the airways. The airway eosinophils were purified and were labeled with a fluorescent dye. The labeled eosinophils were instilled into the mouse tracheas, fluorescent microscope was used to observe the migration of endobronchial eosinophils in vivo. Single cell suspension was prepared from paratracheal lymph nodes of mice receiving antigen-exposed eosinophil instillation, and flow cytometry was used to determine proliferation response of T cells and to identify the subset of responding T cells.

RESULTS

By 8 h after tracheal instillation, labeled eosinophils were visible in the subcapsular region and streaming through the subcapsular sinus (19.0 +/- 1.8/mm(2)). With increasing time, the numbers of eosinophils entering the regional lymph nodes increased, peaking at 24 h (59.2 +/- 7.2/mm(2)) and persisting for at least 120 h (29.6 +/- 2.8/mm(2)). In sensitized mice that received 5 x 10(5) antigen-exposed eosinophils, in vivo percentage of proliferating T cell in the paratracheal lymph nodes 1 d after eosinophil instillation (6.9% +/- 0.5%) were much higher than basic control value (3.2% +/- 0.3%, P < 0.01), peaked at day 3 (10.8% +/- 0.8%, P < 0.01), and then declined over 7 d (6.1% +/- 0.6%, P < 0.05). Eosinophil-induced in vivo T cell proliferation was antigen-specific, and the responding T cells were limited to CD4(+) cells.

CONCLUSIONS

Eosinophils within the lumina of airways can process inhaled antigens, traffick to regional lymph nodes and function in vivo as antigen-presenting cells to stimulate responses of CD4(+) T cells.

Insulin-like growth factors and prostate cancer: a population-based case-control study in China

Insulin-like growth factors (IGFs) have potent mitogenic and antiapoptotic effects on prostate epithelial cells. Through modulation of IGF bioactivity and other mechanisms, IGF-binding proteins (IGFBPs) also have growth-regulatory effects on prostate cells. Recently, IGF-I and IGFBP-3 have been implicated in prostate cancer risk among Western populations. To assess whether IGF-I, IGF-II, IGFBP-1, or IGFBP-3 are also associated with prostate cancer in a low-risk population, we measured plasma levels of these factors among 128 newly diagnosed prostate cancer cases and 306 randomly selected population controls in Shanghai, China. Relative to the lowest quartile of IGF-I levels, men in the highest quartile had a 2.6-fold higher prostate cancer risk, with a significant trend [odds ratio (OR) = 2.63; 95% confidence interval (95% CI) = 1.19-5.79; P(trend) = 0.01]. In contrast, men in the highest quartile of IGFBP-3 levels had a 46% decreased risk relative to the lowest quartile (OR = 0.54; 95% CI = 0.26-1.15; P(trend) = 0.08). A similar but less distinct result was observed for IGFBP-1 (OR = 0.60; 95% CI = 0.31-1.17; P(trend) = 0.25). Men in the highest quartile for the IGF-I:IGFBP-3 molar ratio (an indirect measure of free IGF-I) had a 2.5-fold higher risk compared with the lowest quartile (OR = 2.51; 95% CI = 1.32-4.75, P(trend) < 0.001). These associations were more pronounced after adjustment for serum 5alpha-androstane-3alpha,17beta-diol glucuronide and sex hormone-binding globulin levels. There was no significant association with IGF-II levels. Our findings in a low-risk population provide evidence that IGF-I, IGFBP-3, and IGFBP-1 are determinants of prostate cancer and indicate that additional studies are needed to evaluate their effects on ethnic and geographic incidence differentials and to elucidate carcinogenic mechanisms.

Derivation of electron and photon energy spectra from electron beam central axis depth dose curves

A method for deriving the electron and photon energy spectra from electron beam central axis percentage depth dose (PDD) curves has been investigated. The PDD curves of 6, 12 and 20 MeV electron beams obtained from the Monte Carlo full phase space simulations of the Varian linear accelerator treatment head have been used to test the method. We have employed a 'random creep' algorithm to determine the energy spectra of electrons and photons in a clinical electron beam. The fitted electron and photon energy spectra have been compared with the corresponding spectra obtained from the Monte Carlo full phase space simulations. Our fitted energy spectra are in good agreement with the Monte Carlo simulated spectra in terms of peak location, peak width, amplitude and smoothness of the spectrum. In addition, the derived depth dose curves of head-generated photons agree well in both shape and amplitude with those calculated using the full phase space data. The central axis depth dose curves and dose profiles at various depths have been compared using an automated electron beam commissioning procedure. The comparison has demonstrated that our method is capable of deriving the energy spectra for the Varian accelerator electron beams investigated. We have implemented this method in the electron beam commissioning procedure for Monte Carlo electron beam dose calculations.

Beta-catenin mutations in biliary tract cancers: a population-based study in China

beta-Catenin is an ubiquitously expressed cytoplasmic protein that has a crucial role in both cadherin-mediated cell-cell adhesion and as a downstream signaling molecule in the wingless/Wnt pathway. Activating mutations in exon 3 of the beta-catenin gene, at the phosphorylation sites for ubiquitination and degradation of beta-catenin, are present in a variety of cancers. Because alterations of the adenomatous polyposis coli (APC) gene are present in biliary tract cancers and the APC protein modulates levels of beta-catenin, we evaluated the role of beta-catenin in biliary tract cancer by sequencing the third exon of the beta-catenin gene among 107 biliary tract cancers and 7 gallbladder adenomas from a population-based study in CHINA: Point mutations of serine or threonine phosphorylation sites in exon 3 of beta-catenin were present in 8 of 107 (7.5%) biliary tract cancers and 4 of 7 (57.1%) gallbladder adenomas. Mutations of beta-catenin were more frequent in ampullary and gallbladder carcinomas than in bile duct carcinomas (P = 0.04) and in papillary adenocarcinomas than other histological types of carcinomas (P = 0.02). These results suggest that the molecular pathways of biliary tract neoplasms vary by anatomical subsite and histological subtype.

The MLC tongue-and-groove effect on IMRT dose distributions

We have investigated the tongue-and-groove effect on the IMRT dose distributions for a Varian MLC. We have compared the dose distributions calculated using the intensity maps with and without the tongue-and-groove effect. Our results showed that, for one intensity-modulated treatment field, the maximum tongue-and-groove effect could be up to 10% of the maximum dose in the dose distributions. For an IMRT treatment with multiple gantry angles (> or = 5), the difference between the dose distributions with and without the tongue-and-groove effect was hardly visible, less than 1.6% for the two typical clinical cases studied. After considering the patient setup errors, the dose distributions were smoothed with reduced and insignificant differences between plans with and without the tongue-and-groove effect. Therefore, for a multiple-field IMRT plan (> or = 5), the tongue-and-groove effect on the IMRT dose distributions will be generally clinically insignificant due to the smearing effect of individual fields. The tongue-and-groove effect on an IMRT plan with small number of fields (< 5) will vary depending on the number of fields in a plan (coplanar or non-coplanar), the MLC leaf sequences and the patient setup uncertainty, and may be significant (> 5% of maximum dose) in some cases, especially when the patient setup uncertainty is small (< or = 2 mm).

Prostate cancer, benign prostatic hyperplasia and physical activity in Shanghai, China

BACKGROUND

Studies suggest that increased levels of physical activity might decrease the risk of prostate cancer. We ascertained lifetime measures of activity in a population-based case-control study of prostate cancer in Shanghai, China to investigate physical activity in a population where the incidence of prostate cancer is low but rising.

METHODS

In all, 238 men with prostate cancer, diagnosed 1993-1995, were identified through a rapid reporting system. A second group of 206 men with benign prostatic hyperplasia (BPH) was matched to prostate cancer cases, and 471 age-matched and population-based controls were identified from urban Shanghai. Through personal interviews, we ascertained all daily, occupational, and recreational activities at ages 20-29, ages 40-49, and in 1988 to generate hours spent sleeping, sitting, in moderate activity, and in vigorous activity. Time spent per week in different activities was converted to metabolic equivalents (MET-h) and energy expended.

RESULTS

Time spent in, MET-h of, and energy expended in physical activities were not consistently related to either prostate cancer or BPH when compared to controls. Few men reported regular vigorous activity. Occupational activity, based on an energy expenditure index using job titles, was suggestively associated with a decreased risk of BPH, but not associated with prostate cancer. Associations did not vary according to age or stage of prostate cancer at diagnosis.

CONCLUSIONS

Our results, based on regular physical activity, occupational activity, hours in activities, MET-h, and energy expended, did not support a protective role of physical activity in prostate cancer or BPH for men in a low-risk population.

[Biodegradation behavior of ethylenediaminetetraethylene acid]

Aerobic and anaerobic degradability of ethylenediaminetetraethylene acid(EDTA) were measured on Warburg respirometer and anaerobic batch reactors. Biodegradation of EDTA as a single substance was poor, but biodegradation of EDTA with co-substrate could be improved. The wastewater containing EDTA can be treated by activated sludge process. The EDTA removal efficiency was 80% under the circumstance HRT 16 h and EDTA removal efficiency reached to 92.5%-95.1% when HRT was 20 h. The main factor affecting the biodegradability of EDTA is sludge remained time.

[Correlation of tumor microvessel density with prognosis in laryngopharyngeal malignant melanoma]

OBJECTIVE

To investigate the relationship between microvessel density and clinicopathology, as well as the prognosis in pharyngo-laryngeal malignant melanoma.

METHODS

Specific endothelial cell markers with immunohistochemistry and microvessel density with morphometry in 28 cases of laryngopharyngeal malignant melanoma.

RESULTS

There was no correlation between the microvessel density (MVD) and the tumor size, Clark grade, as well as Breslow grade; however, significant correlation was found between the MVD and the AJC's grade, as well as the proliferating cell nuclear antigen (PCNA) labelling index. Microvessel counts were associated with overall survival by Kaplan-Meier analysis. An average vessel count of less than 36.5 (x 200) suggested a better survival, but a higher vessel count of more than 36.5 (x 200) showed a trend to worse the overall survival.

CONCLUSION

The results suggest a significant relationship between MVD and prognosis; moreover, MVD may be a useful prognostic indicator in laryngopharyngeal malignant melanoma.

Online motion-gated dynamic three-dimensional echocardiography in the fetus--preliminary results

The aim of this study was to visualise the fetal heart in dynamic three dimensions (4-D) during an ultrasound (US) scan (online), rather than after (offline). With special pairing and sequential setting to minimise interference between two scanners, umbilical arterial Doppler waveforms (UADWs) from one scanner were used as an online motion gating source to trigger simultaneous 3-D cardiac structural data acquisition by another. Of 25 data sets from 10 fetuses, 18 were acquired in 15 to 30 s per set with > or = 50% Doppler waveforms efficiently converted to triggering signals. Of 15 valid 4-D data sets, 10 were reconstructed in 2 to 20 min, compared to over 2 h previously reported (mainly for offline gating). Fine structures (including chordae tendinae and trabecular muscles) were depicted in six sets. The main problems in degrading 4-D images were extensive shadowing (6) from bony structures during rigid mechanical scanning, and random motion artefacts (6) from prolonged setting-up time with a complex combination of several systems. Integration of these systems is, therefore, recommended.

Conversion of umbilical arterial Doppler waveforms to cardiac cycle triggering signals: a preparatory study for online motion-gated three-dimensional fetal echocardiography

To remove motion artefacts, a device was built to convert "noisy" umbilical arterial Doppler waveforms (UADWs) from an ultrasound (US) system into sharp ECG R-wave-like cardiac cycle triggering signals (CCTSs). These CCTSs were then used to gate a simultaneous (online) 3-D acquisition of sectional fetal echocardiograms from another US system. To test the conversion performance, a study was carried out in sheep fetal twins. Pulmonary arterial flow waveforms (PAFWs) from implanted probes were traced, in the meantime, to determine the reference cardiac cycle. Interference caused by running the two nonsynchronised US systems was controlled to three degrees (not-noticeable, moderate, and severe), together with high (> or = 40 cm/s) and low (< 40) flow velocities on UADWs. The conversion efficiency, assessed by the percentage of UADWs converted into CCTSs, was in the range of 83% to 100% for not-noticeable and moderate interference, and 0% to 71% for severe interference. The triggering accuracy, assessed by [(time lag mean between the onsets of PAFWs and corresponding CCTSs) -- (its 99% confidence level)] / the mean, was 90% to 96% for the not-noticeable interference high- and low-flow groups and for the moderate interference high-flow group; 19% to 93% for the moderate interference low-flow group; and from not obtainable up to 90% for the severe interference groups. The results show that UADWs can be used as a satisfactory online motion-gating source even in the presence of moderate interference. The major problems are from severe interference or moderate interference with low-flow velocity, which can be minimised/eliminated by the integration of the individual systems involved.

Characterization for didodecyldimethylammonium bromide liquid crystal film entrapping catalase with enhanced direct electron transfer rate

Direct electrochemistry for catalase (CAT) embedded in the liquid crystal film of didodecyldimethylammonium bromide (DDAB) was investigated at pyrolytic graphite (PG) electrode by voltammetric methods. The reduction reaction involved the redox couple in CAT, i.e. FeIII/FeII couple. The electron transfer between the incorporated CAT and PG electrode was found to be greatly enhanced by DDAB. The heterogeneous electron transfer rate constant k(s) was fitted as 3.0 +/- 0.4 s(-1) using the nonlinear regression analysis of the square wave voltammograms at a series of pulse heights. The pH dependence of the formal potential for CAT in DDAB film was 57 mV/pH, which suggested one-proton-transfer together with a one-electron reaction. Visible absorption and reflectance-absorbance infrared (RAIR) spectra inferred the similar heme environment of CAT in DDAB film to its native status. Circular dichroism (CD) results indicated DDAB affected slightly on the second structure of CAT.