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Mueller WH, Dai S, Labarthe DR. Tracking body fat distribution during growth: using measurements at two occasions vs one. Int J Obes (Lond) 2001; 25:1850-5. [PMID: 11781767 DOI: 10.1038/sj.ijo.0801832] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2001] [Revised: 05/15/2001] [Accepted: 06/13/2001] [Indexed: 01/05/2023]
Abstract
OBJECTIVE To investigate whether within-individual variation is a factor in the generally reported poor tracking of central body fat distribution (CBFD) during development and whether two measurements of CBFD during each measurement occasion would improve the estimate of tracking over time. METHODS A longitudinal study compared the results of two measurements of body fat (BF) and CBFD during each measurement occasion to the results of one measurement of BF and CBFD during each occasion every 4 months over 1-3 y. A total of 345 boys and 333 girls in three age cohorts of 8, 11 and 14 y at baseline were examined. BF variables were: body mass index (BMI); fat mass and percentage body fat from bioelectrical impedance; two skinfold sums; and abdominal circumference. CBFD variables were: waist/hip and waist/thigh ratios; conicity; and log upper-lower skinfold ratio. RESULTS Three-year tracking of BF varied from 0.79 to 0.90 for one- and from 0.81 to 0.93 for two-occasion measurements showing no apparent sex- or cohort-effects. Three-year tracking of CBFD was lower than that of BF (0.68-0.75), but improved significantly with two-occasion measurements (0.75-0.82). CONCLUSIONS Within-individual variation is a significant factor in reported low tracking of CBFD in childhood. Estimates of tracking currently in the literature may underestimate the predictive value of CBFD, possibly because this research has used one-occasion measurement. The increased use of two-occasion measurement should significantly improve the tracking of CBFD during development and provide a more realistic understanding of its predictive value.
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Burleigh M, Dai S, Barnes C, Xue Z. ENHANCED IONIC RECOGNITION BY A FUNCTIONALIZED MESOPOROUS SOL-GEL: SYNTHESIS AND METAL ION SELECTIVITY OF DIAMINOETHANE DERIVATIVE. SEP SCI TECHNOL 2001. [DOI: 10.1081/ss-100107910] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
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128
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Wang Q, Wang K, Dai S, Yang Y, Chen Y, Mo Z. [Regulation on the immunological effect of mogrosides in mice]. ZHONG YAO CAI = ZHONGYAOCAI = JOURNAL OF CHINESE MEDICINAL MATERIALS 2001; 24:811-2. [PMID: 15575165] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/01/2023]
Abstract
OBJECTIVE To investigate the cellular immunological effect of mogrosides in mice. METHODS Mogrosides was administered to normal or CTX-induced immunosuppressive mice, and their macrophage function and T lymphocyte proliferation were detected. RESULTS Mogrosides could promote phagocytosis and T lymphocyte proliferation significantly in the CTX-induced immunosuppressive mice, but not in the normal mice. CONCLUSION The results suggested that mogrosides had certain up-regulation on cellular immunity in the CTX-induced immunosuppressive mice.
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129
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Dai S, Tam KC. Isothermal Titration Calorimetry Studies of Binding Interactions between Polyethylene Glycol and Ionic Surfactants. J Phys Chem B 2001. [DOI: 10.1021/jp0110354] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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130
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Dai S, Tam KC, Jenkins RD. Binding Characteristics of Hydrophobic Ethoxylated Urethane (HEUR) and an Anionic Surfactant: Microcalorimetry and Laser Light Scattering Studies. J Phys Chem B 2001. [DOI: 10.1021/jp010672r] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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131
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Zhang Z, Dai S. Preparation and characterization of novel inorganic-organic mesoscopic ordered composites with bridges formed by coordination compounds. J Am Chem Soc 2001; 123:9204-5. [PMID: 11552846 DOI: 10.1021/ja0158556] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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132
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Zhang Q, Xiong Y, Li D, Dai S. [A simple and rapid procedure for detection of DNA damage caused by Aldicarb]. HUAN JING KE XUE= HUANJING KEXUE 2001; 22:126-8. [PMID: 11769219] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
A simple and rapid procedure for detection of low levels DNA damage caused by Aldicarb was developed and compared with some other methods. In the original position the gel was set in high-pH buffer to run electrophoresis after the diluent of bacteria or fragmentized organ was added into hole of agarose gel directly and cells were treated with detergent and high alkaline condition. The impact of Aldicarb to biological individual or ecosystem was assessed according to the quantity of DNA and the extent of DNA migration.
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133
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Wu L, Zhang H, Zhu H, Zhang Z, Zhuang Y, Dai S. [Sulfa-drug wastewater treatment with anaerobic/aerobic process]. HUAN JING KE XUE= HUANJING KEXUE 2001; 22:87-90. [PMID: 11769237] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
Sulfa drug wastewater was treated with anaerobic/aerobic process. The removal ratios of TOC reached about 50% in anaerobic phase and about 70% in aerobic phase respectively, while volume loading rate of TOC was about 1.2 kg/(m3.d) in anaerobic phase and about 0.6 kg/(m3.d) in aerobic phase. Removal of TOC in anaerobic phase was attributed to the reduction of sulfate.
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134
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Koffman MD, Dai S. Cholesterol screening. BUSINESS AND HEALTH 2001; 19:42. [PMID: 11569315] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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135
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Dai S, Tam KC, Li L. Isothermal Titration Calorimetric Studies on Interactions of Ionic Surfactant and Poly(oxypropylene)−Poly(oxyethylene)− Poly(oxypropylene) Triblock Copolymers in Aqueous Solutions. Macromolecules 2001. [DOI: 10.1021/ma010329k] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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136
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Dai S, Best S, St John M. Bartonella henselae neuroretinitis in cat scratch disease. THE NEW ZEALAND MEDICAL JOURNAL 2001; 114:360-1. [PMID: 11587306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/21/2023]
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137
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Wang P, Dai S, Waezsada SD, Tsao AY, Davison BH. Enzyme stabilization by covalent binding in nanoporous sol-gel glass for nonaqueous biocatalysis. Biotechnol Bioeng 2001; 74:249-55. [PMID: 11400098 DOI: 10.1002/bit.1114] [Citation(s) in RCA: 171] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
A unique nanoporous sol-gel glass possessing a highly ordered porous structure (with a pore size of 153 A in diameter) was examined for use as a support material for enzyme immobilization. A model enzyme, alpha-chymotrypsin, was efficiently bound onto the glass via a bifunctional ligand, trimethoxysilylpropanal, with an active enzyme loading of 0.54 wt%. The glass-bound chymotrypsin exhibited greatly enhanced stability both in aqueous solution and organic solvents. The half-life of the glass-bound alpha-chymotrypsin was >1000-fold higher than that of the native enzyme, as measured either in aqueous buffer or anhydrous methanol. The enhanced stability in methanol, which excludes the possibility of enzyme autolysis, particularly reflected that the covalent binding provides effective protection against enzyme inactivation caused by structural denaturation. In addition, the activity of the immobilized alpha-chymotrypsin was also much higher than that of the native enzyme in various organic solvents. From these results, it appears that the glass-enzyme complex developed in the present work can be used as a high-performance biocatalyst for various chemical processing applications, particularly in organic media. Published by John Wiley & Sons
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138
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Petruccelli S, Dai S, Carcamo R, Yin Y, Chen S, Beachy RN. Transcription factor RF2a alters expression of the rice tungro bacilliform virus promoter in transgenic tobacco plants. Proc Natl Acad Sci U S A 2001; 98:7635-40. [PMID: 11390974 PMCID: PMC34720 DOI: 10.1073/pnas.121186398] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/16/2001] [Indexed: 11/18/2022] Open
Abstract
The promoter from rice tungro bacilliform badnavirus (RTBV) is expressed only in phloem tissues in transgenic rice plants. RF2a, a b-Zip protein from rice, is known to bind to the Box II cis element near the TATA box of the promoter. Here, we report that the full-length RTBV promoter and a truncated fragment E of the promoter, comprising nucleotides -164 to +45, result in phloem-specific expression of beta-glucuronidase (GUS) reporter genes in transgenic tobacco plants. When a fusion gene comprising the cauliflower mosaic virus 35S promoter and RF2a cDNA was coexpressed with the GUS reporter genes, GUS activity was increased by 2-20-fold. The increase in GUS activity was positively correlated with the amount of RF2a, and the expression pattern of the RTBV promoter was altered from phloem-specific to constitutive. Constitutive expression of RF2a did not induce morphological changes in the transgenic plants. In contrast, constitutive overexpression of the b-ZIP domain of RF2a had a strong effect on the development of transgenic plants. These studies suggest that expression of the b-Zip domain can interfere with the function of homologues of RF2a that regulate development of tobacco plants.
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139
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Dai S, Liu G, Qian Y, Cheng X. The sorption behavior of complex pollution system composed of aldicarb and surfactant--SDBS. WATER RESEARCH 2001; 35:2286-2290. [PMID: 11358309 DOI: 10.1016/s0043-1354(00)00491-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The behavior of complex pollution system in soil composed of aldicarb, a carbamate pesticide, and sodium dodecylbenzenesulfonate (SDBS), an anionic surfactant, was studied by the experiment of shaking sorption balance. The range of concentration of aldicarb and SDBS was 0.4-5.0 and 1-1000 mg/kg of dried soil, respectively. Linear sorption isotherm was well fitted for these two chemicals. SDBS can decrease the sorption of aldicarb in soil remarkably. While the concentration of SDBS increased from 0 to 1000 mg/kg, the linear sorption coefficient can be decreased by 50%. But aldicarb showed no effect on the sorption of SDBS in experiment. In addition the mechanism of the effect of SDBS on sorption of aldicarb was discussed.
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140
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Zhang X, Chen J, Peng Q, Wang D, Ma W, Dai S, Chen D. [Analysis of the lineshape of laser frequency modulation]. GUANG PU XUE YU GUANG PU FEN XI = GUANG PU 2001; 21:257-262. [PMID: 12947640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In this paper, we analyze the dependence of the output signal spectral lineshape and intensity on the modulation, waveform and modulation index in first- and second-harmonic detection of triangle modulation, square demodulation and saw modulation square demodulation. The signal lineshape in the case of saw modulation, square demodulation is quite different from, whereas the signal lineshape in the case of triangle modulation, square demodulation is similar to that in traditional sine modulation, sine demodulation. Experiments of tunable IR laser frequency modulation absorption spectrum of methane are also done to verify the theoretical analysis. Then we reach a conclusion; the lineshape and intensity of frequency modulation spectrum can be influenced by modulation waveform, demodulation waveform and modulation index. Calculation results can be used to choose better experimental parameters and optimize experimental designs.
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141
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Dai S, Tam KC, Jenkins RD. Microstructure of Dilute Telechelic Associative Polymer in Sodium Dodecyl Sulfate Solutions. Macromolecules 2001. [DOI: 10.1021/ma0100807] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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142
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Nie Y, Li Y, Sha W, Dai S, She Q, Wu H. [Effect of octreotide on intragastric pH in patients with duodenal ulcer bleeding]. ZHONGHUA YI XUE ZA ZHI 2001; 81:520-2. [PMID: 11809113] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
OBJECTIVE To evaluate the effect of octreotide on the intragastric pH of patients with duodenal ulcer bleeding during the period of 24 hours and to observe if it can advance the effect of hemostasis by endoscopic injection of epinephrine. METHODS Twenty-four patients with duodenal ulcer bleeding were randomly divided into three groups, eight in each. Patients in group 1 received an intravenous injection of 0.1 mg of octreotide followed by continuous intravenous drip of octreotide at a constant speed of 25 microg/h for 24 hours. The patients in group 2 received an intravenous injection of 0.1 mg of octreotide followed by continuous intravenous drip of octreotide at a constant speed of 42 microg/h for 24 hours. The patients in group 3 received an intravenous injection of 40 mg of omeprazole followed by continuous intravenous drip of omeprazole at a constant speed of 8 mg/h for 24 hours. Intragastric pH was continuously recorded with a pH meter. The patients with active ulcer bleeding was treated with injection of epinephrine via endoscope and then received intravenous drip of octreotide (with the same dosage as in group 1, n = 42) or omeprazole (with the same dosage as in group 3, n = 54) for 72 hours and were given omeprazole (20 mg Bid). RESULTS The mean and median intragastric pH values among the patients in group 2 treated by a larger dosage of octreotide (6.7 +/- 0.5 and 6.9 +/- 0.4) were similar to those in the group 3 treated by omeprazole (6.8 +/- 0.4 and 7.0 +/- 0.4). There was no statistically significant difference between these two groups in percentage of intragastric pH above 4, 6, and 7 The mean and median of intragastric pH among the patients in group 1 treated by a smaller dosage of octreotide were statistically significantly smaller (5.2 +/- 0.5 and 5.4 +/- 0.4) than those in the omeprazole group. There was no statistically significant difference between octreotide treatment and omeprazole treatment in terms of volume of blood transfusion (0.7 +/- 0.5 vs. 0.6 +/- 0.4 L), rebleeding rate (11.6% vs. 12.9%), emergency operation rate (7.1% vs. 3.7%), and mortality (2.3% vs. 3.7%). CONCLUSION Octreotide effectively inhibits the secretion of gastric acid. However, the dosage in common use clinically fails to increase the intragastric pH to the best situation needed for effective hemostasis. Only a large dosage (1.10 mg/d) works.
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Abstract
A double imprinting methodology was developed to synthesize novel materials with hierarchical structures. On the microporous level (1-3 A), metal ions served as template. On the mesoporous level (diameters of 25-40 A), micellar structures produced by self-assembly of surfactant molecules were used as templates. Removal of both metal ions and surfactant micelles resulted in the formation of imprints with different sizes within the silica matrix, each with a specific function. This research opens vast opportunities for the applications of ordered mesoporous materials in the area of molecular recognition such as separations, chemical sensors, and catalysts.
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144
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Dai S, Tam KC, Jenkins RD. Light Scattering of Hydrophobically Modified Alkali-Soluble Emulsion (HASE) Polymer: Ionic Strength and Temperature Effects. MACROMOL CHEM PHYS 2001. [DOI: 10.1002/1521-3935(20010101)202:2<335::aid-macp335>3.0.co;2-h] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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145
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Xin B, Zhuang Y, Zou Q, Dai S, Song W. [Adsorption of anthraquinone dyes by biosorbent GX2]. HUAN JING KE XUE= HUANJING KEXUE 2001; 22:14-8. [PMID: 11382034] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
The GX2 growing mycelium shows excellent adsorptive capacity on the four kinds of anthraquinone dyes, however, due to the difference of molecular structure of dyes, the adsorption rates are different. Although the dyes show inhibiting effect on the growth of GX2, when the concentration of reactive brilliant blue KN-R is 250 and 400 mg/L, the adsorption rate of dye by the GX2 growing mycelium reaches 100% and 91.4%, respectively. With the increase of salinity (NaCl), the dry weight of GX2 mycelium increases; the diameter of granular mycelium decreases and its adsorption surface area increases accordingly, the salinity shows evident enhancement on the adsorption of reactive brilliant blue KN-R by GX2 growing mycelium in the range of 0%-2% salinity. The adsorption process is influenced by the concentration of carbon source as well, reactive brilliant blue KN-R with the concentration of 120 mg/L can be completely adsorbed only when the concentration of glucose is more than 2.5 g/L. The GX2 growing mycelium has better adsorptive capacity than resting living mycelium and dead mycelium.
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146
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Xi Z, Dai S, Sun Y. [The bindings of typical aldehydes pollutants with cell DNA]. HUAN JING KE XUE= HUANJING KEXUE 2001; 22:19-22. [PMID: 11382035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/20/2023]
Abstract
The bindings of 3 kinds of aidehyde pollutants, formaldehyde, acetaldehyde, acrolein, with both prokaryotic and eukaryotic DNA, and their genotoxic effect and mechanism were conducted by the shifts of maximum UV absorption peak to determine binding effects and by HPLC to determine binding sites in vitro model system. The shifts of maximum UV absorption peak of prokaryotic DNA contaminated by 3 kinds of aldehyde pollutants are not significant; but after the DNA extracted from prokaryotic bacteria reacting with formaldehyde in tube, the shifts of maximum UV absorption peak of DNA are significant; the shifts of maximum UV absorption peak of eukaryotic DNA contaminated by 3 kinds of aldehyde pollutants are significant also. The reacition of acetaldehyde with dG reduced by NaBH4 was separated and detected by HPLC, the product was determined qualitatively as N2-ethaldeoxyguanosine adduct. The 3 kinds of aldehyde pollutants could bind with cellular DNA to express genotoxic effects; and the N2 site of deoxyguanosine is the possible covalent binding site.
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147
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Wallace SA, Hiller JM, Dai S, Miller LF. Neutron detection based upon a lithiated sol-gel glass. Appl Radiat Isot 2000; 53:755-8. [PMID: 11003516 DOI: 10.1016/s0969-8043(00)00222-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The addition of dopants in the wet chemistry formation of glass in sol-gel technology is used for many purposes. Among the uses are the fabrication of films sensitive to pH, temperature, the presence of dissolved chemicals in solutions and many others. This paper describes the use of sol-gel technology for the doping of B-10, Li-6 and U-235 into glass films applied to silicon surface barrier (SSB) detectors. Using a commercial preamp/amplifier and an IEEE-488 NIM counter, the response was recorded of the neutron profile in a neutron activation source. A portable personal computer recorded the thermal neutron map as the detector was lowered in 1.27-cm steps down a Numec thermal neutron activation source. The lithiated glass film on the SSB gave about four times the count rate of the boron-10 doped glass film. The U-235 doped glass film gave a much lower count rate, but maintained a constant output signal due to the presence of the alpha activity from the U-235 and the trace of U-234 present in the sample.
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Lin Y, Sun H, Dai S, Tang Z, He X, Chen H. The bi-directional regulation of filamin on the ATPase activity of smooth muscle myosin. CHINESE MEDICAL SCIENCES JOURNAL = CHUNG-KUO I HSUEH K'O HSUEH TSA CHIH 2000; 15:162-4. [PMID: 12903776] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/21/2023]
Abstract
OBJECTIVE The aim of this study is to investigate the functional relationship between filamin, a known actin binding protein, and myosin and the effects of filamin on the interaction between myosin and actin. METHODS Ultra-centrifugation method was used to investigate the binding of filamin to both phosphorylated and unphosphorylated myosins. Mg-ATPase activities of both phosphorylated and unphosphorylated myosins in the presence and absence of actin were measured to observe the effects resulted from filamin-actin and filamin-myosin interactions. RESULTS It was found that filamin is also a myosin binding protein. Filamin inhibited the actin activated Mg-ATPase activity of phosphorylated myosin and stimulated Mg-ATPase of phosphorylated myosin in the absence of actin; in addition, filamin stimulated Mg-ATPase activity of unphosphorylated myosin in both the presence or absence of actin. CONCLUSION The result suggest that the effects of filamin on the myosin Mg-ATPase activities are bi-directional, i.e., stimulatory via binding to myosin and inhibitory via binding to actin.
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Dai S, Tam KC, Jenkins RD, Bassett DR. Light Scattering of Dilute Hydrophobically Modified Alkali-Soluble Emulsion Solutions: Effects of Hydrophobicity and Spacer Length of Macromonomer. Macromolecules 2000. [DOI: 10.1021/ma000528o] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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150
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Dai S, Ye Q, Wang E, Meyerhoff ME. Optical detection of polycations via polymer film-modified microtiter plates: response mechanism and bioanalytical applications. Anal Chem 2000; 72:3142-9. [PMID: 10939379 DOI: 10.1021/ac000060n] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Microtiter plate wells modified with thin (approximately 20 microm) polymeric films capable of optically sensing macromolecular protamine and other polycationic species are described. The plates are prepared by coating the bottom of each well of a conventional 96-well polypropylene plate with an adherent polymer film (a mixture of poly(vinyl chloride) and polyurethane) containing a lipophilic 2',7'-dichlorofluorescein derivative. Surprisingly, optical response toward polycations is shown to result from the extraction of the fluorescein derivative from the polymer film into a lyophobic colloidal phase at the sample/film interface. This new phase is likely composed of a micellular-type ion pair complex between the analyte polycation from aqueous sample phase and the deprotonated form of the fluorescein derivative. Accumulation of the deprotonated fluorescein species in this interfacial region induces an absorbance change measured at 540 nm. Optimized plates can be used to sense protamine concentrations in the range of 0-100 microg/mL in 10 min with little or no response to physiological levels of common cationic species (Na+, K+, Ca2+, etc.). The modified plates are shown to be useful as simple optical detectors for measuring heparin levels in plasma via titrations with protamine and for monitoring protease activities (trypsin and plasmin) that cleave polycationic peptides/proteins such as protamine into smaller peptide fragments that are not detected by the sensing films. Assays for "clot busting" plasminogen activators (streptokinase, urokinase, and tissue plasminogen activator) are also demonstrated using this relatively simple microtiter plate-based polycation detection system.
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