101
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Dai S, Keenan NL, Croft JB, Greenlund KJ, Labarthe DR. 035: Racial/Ethnic Disparities in Premature Death from the Leading Causes of Death in the United States, 2000. Am J Epidemiol 2005. [DOI: 10.1093/aje/161.supplement_1.s9b] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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102
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Zhang Z, Rondinone AJ, Ma JX, Shen J, Dai S. Morphologically Templated Growth of Aligned Spinel CoFe 2 O 4 Nanorods. ADVANCED MATERIALS (DEERFIELD BEACH, FLA.) 2005; 17:1415-1419. [PMID: 34412436 DOI: 10.1002/adma.200500009] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2005] [Accepted: 03/07/2005] [Indexed: 06/13/2023]
Abstract
Uniaxially aligned CoFe2 O4 nanorods are obtained by coprecipitation of Co2+ , Fe2+ , and C2 O4 2- ions in a microemulsion solution, and subsequent high-temperature decomposition of CoFe2 (C2 O4 )3 . Each nanorod is made up of a "tectonic" assembly of CoFe2 O4 nanocrystals. Magnetization of such CoFe2 O4 materials may lead to their use in high-density magnetic recording media and high-performance electromagnetic and spintronic devices.
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103
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Tang Z, Chen H, Yang J, Dai S, Lin Y. The comparison of Ca2+/CaM-independent and Ca2+/CaM-dependent phosphorylation of myosin light chains by MLCK. Physiol Res 2005; 54:671-8. [PMID: 15717857] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/01/2023] Open
Abstract
The main regulatory mechanism of smooth muscle contraction involves Ca2+/calmodulin (CaM)-dependent phosphorylation of myosin (CDPM), by myosin light chain kinase (MLCK). It is also known that the increase in intracellular Ca2+ and phosphorylation of myosin occurs within a short time under physiological conditions, but the muscle tension may persist for a longer period of time. However, the mechanism of this phenomenon is still not clear. We hypothesize that MLCK also phosphorylates myosin in a Ca2+/CaM-independent manner (CIPM). The difference between CIPM and CDPM are as follows. Firstly, the extent of CIPM by MLCK was temperature-independent, whereas CDPM by MLCK was apparently decreasing with increasing temperature. Secondly, in contrast to the decreased extent of CDPM, the prolongation of incubation time did not decrease the extent of CIPM. Thirdly, a high concentration of K+ influences CIPM less than CDPM. Furthermore, the MLCK inhibitor ML-9 significantly inhibited CDPM by MLCK but not CIPM by MLCK. Lastly, arachidonic acid selectively increased CIPM by MLCK but not CDPM by MLCK. Finally, the activity of Mg2+-ATPase of myosin followed the sequence as this: CDPM>CIPM>unphosphorylated myosin. Our results revealed some primary features of CIPM by MLCK.
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104
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Tang Z, Chen H, Yang J, Dai S, Lin Y. The comparison of Ca2+/CaM-independent and Ca2+/CaM-dependent phosphorylation of myosin light chains by MLCK. Physiol Res 2005. [DOI: 10.33549/physiolres.930719] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
The main regulatory mechanism of smooth muscle contraction involves Ca2+/calmodulin (CaM)-dependent phosphorylation of myosin (CDPM), by myosin light chain kinase (MLCK). It is also known that the increase in intracellular Ca2+ and phosphorylation of myosin occurs within a short time under physiological conditions, but the muscle tension may persist for a longer period of time. However, the mechanism of this phenomenon is still not clear. We hypothesize that MLCK also phosphorylates myosin in a Ca2+/CaM-independent manner (CIPM). The difference between CIPM and CDPM are as follows. Firstly, the extent of CIPM by MLCK was temperature-independent, whereas CDPM by MLCK was apparently decreasing with increasing temperature. Secondly, in contrast to the decreased extent of CDPM, the prolongation of incubation time did not decrease the extent of CIPM. Thirdly, a high concentration of K+ influences CIPM less than CDPM. Furthermore, the MLCK inhibitor ML-9 significantly inhibited CDPM by MLCK but not CIPM by MLCK. Lastly, arachidonic acid selectively increased CIPM by MLCK but not CDPM by MLCK. Finally, the activity of Mg2+-ATPase of myosin followed the sequence as this: CDPM > CIPM > unphosphorylated myosin. Our results revealed some primary features of CIPM by MLCK.
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105
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Dai S, Ravi P, Tan CH, Tam KC. Self-assembly behavior of a stimuli-responsive water-soluble [60]fullerene-containing polymer. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:8569-8575. [PMID: 15379476 DOI: 10.1021/la048826s] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
A novel pH- and temperature-responsive water-soluble [60]fullerene-containing poly[2-(dimethylamino)ethyl methacrylate] (C60-b-PDMAEMA) was synthesized by atom transfer radical polymerization. The pH and temperature dependence of the physical properties of the aqueous C60-b-PDMAEMA solution was studied by potentiometric and conductometric titrations, UV-vis transmittance, and laser light scattering techniques. At low pH and at temperatures ranging from 25 to 55 degrees C, in addition to C60-b-PDMAEMA unimers, micelle-like aggregates are produced in the aqueous solution containing C60 hydrophobic cores and protonated PDMAEMA shells. Only unimeric C60-b-PDMAEMAs are found to exist in solution at high pH and low temperature, where PDMAEMA segments form a charge-transfer complex with C60 molecules. However, C60-b-PDMAEMA precipitates from aqueous solution at temperatures exceeding the lower critical solution temperature of PDMAEMA of approximately 45 degrees C. The pH and temperature stimuli-responsive properties of the [60]fullerene-containing polymer in aqueous solution are completely reversible.
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106
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Dai S, Tam KC, Wyn-Jones E, Jenkins RD. Isothermal Titration Calorimetric and Electromotive Force Studies on Binding Interactions of Hydrophobic Ethoxylated Urethane and Sodium Dodecyl Sulfate of Different Molecular Masses. J Phys Chem B 2004. [DOI: 10.1021/jp037144v] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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107
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Dai S, Tam KC. Isothermal titration calorimetric studies on the temperature dependence of binding interactions between poly(propylene glycol)s and sodium dodecyl sulfate. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2004; 20:2177-83. [PMID: 15835668 DOI: 10.1021/la0357559] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Isothermal titration calorimetry (ITC) is a sensitive research tool for examining the binding interactions between surfactant and polymer where the differential enthalpy during the binding process is monitored. In addition to the critical micelle concentration (cmc) and the micellization enthalpy (deltaHm), the effective micellar charge fraction (beta) of the ionic surfactant micellization process can also be determined from ITC thermograms. Poly(propylene glycol) (PPG) exhibits a lower critical solution temperature (LCST) ranging from 15 to 42 degrees C, depending on the molecular weights. We report, for the first time, the binding interactions between sodium dodecyl sulfate (SDS) and 1,000, 2,000 and 3,000 Da PPGs, where different binding mechanisms are in operation, depending on the temperature. At temperatures lower than the LCST, the binding interactions are similar to those of SDS and low molecular weight poly(ethylene glycol)s (MW < 3500 Da). At temperatures greater than the LCST, the binding interactions are dominated by direct solubilization of PPG chains into mixed micellar cores. At temperatures near the LCST, the binding interactions are controlled by the balance ofthe PPG solubilization at low SDS concentrations and polymer-induced micellization at high SDS concentrations.
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108
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Bao L, Mahurin SM, Haire RG, Dai S. Silver-Doped Sol−Gel Film as a Surface-Enhanced Raman Scattering Substrate for Detection of Uranyl and Neptunyl Ions. Anal Chem 2003; 75:6614-20. [PMID: 16465717 DOI: 10.1021/ac034791+] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A surface-enhanced Raman scattering (SERS) substrate containing silver particles was prepared by an acid-catalyzed sol-gel method. Silver nitrate was first doped into the sol-gel film followed by chemical reduction of the silver ions with sodium borohydride to produce silver particles. This silver-doped sol-gel substrate exhibits strong enhancement of Raman scattering from adsorbed uranyl ions with a detection limit of 8.5 x 10(-8) M, which is comparable to existing methods of uranyl detection such as spectrophotometry, fluorometry, and a SERS method based on ligand-modified solution silver colloids. However, in the present method, no preconcentration steps, chromogens, or complexing ligands are needed. Compared with the SERS method using Ag colloidal sols, the silver-doped sol-gel film has the advantage that the silver particles trapped in the sol-gel matrix are much more stable than Ag colloids in liquid media. Furthermore, porous silica sol-gel materials are known to have affinities toward many inorganic and organic molecules. The enhanced adsorption affinities could also lead to the increased SERS sensitivity. The performance of the new silver-doped sol-gel substrate was evaluated with uranyl ions and compared to that of a SERS substrate based on silver-coated silica beads prepared by vacuum deposition. The detection limit for the silver-doped sol-gel film was 104 times lower than that for the silver-coated silica beads. The sol-gel substrate was further used to obtain, for the first time, the surface-enhanced Raman spectrum of neptunyl ions in dilute aqueous solutions.
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109
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Dai S, Tam K. Isothermal titration calorimetric studies of alkyl phenol ethoxylate surfactants in aqueous solutions. Colloids Surf A Physicochem Eng Asp 2003. [DOI: 10.1016/j.colsurfa.2003.09.007] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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110
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Manieri W, Franchini L, Raeber L, Dai S, Stritt-Etter AL, Schürmann P. N-terminal truncation of the variable subunit stabilizes spinach ferredoxin:thioredoxin reductase. FEBS Lett 2003; 549:167-70. [PMID: 12914945 DOI: 10.1016/s0014-5793(03)00811-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The variable subunit of spinach ferredoxin:thioredoxin reductase (FTR) has an extended N-terminus compared to FTRs from other sources and this was proposed to contribute to the instability of the protein. We constructed two N-terminal truncation mutants of recombinant FTR by removing 16 or 24 residues from the variable subunit. The mutant proteins are readily expressed and show half-saturation values (S(0.5)) for ferredoxin and thioredoxin f comparable to WT. However, truncation increases significantly their stability. Using the stabilized FTR an exposed Cys on its thioredoxin contact surface could be substituted without altering its properties, whereas the replacement of an active site Cys by Ser completely destabilized the protein.
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111
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Dai S, Sio ST, Tam KC, Jenkins RD. Rheology and Aggregation Behavior of Hydrophobically Modified Urethane Ethoxylate in Ethylene Glycol−Water Mixtures. Macromolecules 2003. [DOI: 10.1021/ma025728+] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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112
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Song T, Dai S, Tam K, Lee S, Goh S. Aggregation behavior of two-arm fullerene-containing poly(ethylene oxide). POLYMER 2003. [DOI: 10.1016/s0032-3861(03)00107-1] [Citation(s) in RCA: 59] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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113
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Dai S, Tam KC, Jenkins RD. Dynamic Light Scattering of Semi-Dilute Hydrophobically Modified Alkali-Soluble Emulsion Solutions with Varying Length of Hydrophobic Alkyl Chains. MACROMOL CHEM PHYS 2002. [DOI: 10.1002/macp.200290004] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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114
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Zhang ZT, Konduru M, Dai S, Overbury SH. Uniform formation of uranium oxide nanocrystals inside ordered mesoporous hosts and their potential applications as oxidative catalysts. Chem Commun (Camb) 2002:2406-7. [PMID: 12430463 DOI: 10.1039/b204987b] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Highly dispersed uranium oxide nanocrystals supported on ordered mesoporous silica matrixes with large surface areas and porosities have been synthesized via a co-assembly methodology; the preliminary catalysis tests showed that these materials have a high catalytic activity for the thermal oxidation of volatile organic compounds (VOCs).
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115
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Xu W, Dai S, Toth LM, Del Cul GD, Peterson JR. Green Upconversion Emission from Er3+ Ion Doped into Sol-Gel Silica Glasses under Red Light (647.1 nm) Excitation. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100013a013] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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116
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Dai S, Toth LM, Del Cul GD, Metcalf DH. Visible and near-IR spectroscopic studies of uranium(IV) oxychloride in a MgCl2-KCl melt. Inorg Chem 2002. [DOI: 10.1021/ic00105a066] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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117
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Pan Q, Petit-Frére C, Dai S, Huang P, Morton HC, Brandtzaeg P, Hammarström L. Regulation of switching and production of IgA in human B cells in donors with duplicated alpha1 genes. Eur J Immunol 2001; 31:3622-30. [PMID: 11745382 DOI: 10.1002/1521-4141(200112)31:12<3622::aid-immu3622>3.0.co;2-h] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
IgA is the predominant immunoglobulin class synthesized in humans and can be subdivided into two subclasses, IgA1 and IgA2, each encoded by a separate gene and differentially expressed depending on age and anatomical localization of the producing cells. Duplication of the alpha1 gene is frequently observed in selected populations. As this duplication may serve to enhance IgA-mediated immunity, we determined its effect on switching and production of IgA in human B cells. We developed a nested PCR strategy, involving sequencing the switch (S) alpha2 region, the only human S region not sequenced to date, to assess the proportion of cells switching to IgA1 and IgA2 in vivo. Our results show that there is no difference in the serum and salivary levels of IgA1 and IgA or rate of switching to IgA1 and IgA between normal donors and individuals carrying alpha1 gene duplications, suggesting involvement of a regulatory step in the production of IgA.
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118
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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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119
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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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120
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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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121
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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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122
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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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123
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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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124
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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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125
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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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