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El-Bourawi M, Ding Z, Ma R, Khayet M. A framework for better understanding membrane distillation separation process. J Memb Sci 2006. [DOI: 10.1016/j.memsci.2006.08.002] [Citation(s) in RCA: 936] [Impact Index Per Article: 49.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19 |
936 |
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Ding Z, Lu GQ, Greenfield PF. Role of the Crystallite Phase of TiO2 in Heterogeneous Photocatalysis for Phenol Oxidation in Water. J Phys Chem B 2000. [DOI: 10.1021/jp993819b] [Citation(s) in RCA: 521] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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25 |
521 |
3
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Huang WM, Yang B, Zhao Y, Ding Z. Thermo-moisture responsive polyurethane shape-memory polymer and composites: a review. ACTA ACUST UNITED AC 2010. [DOI: 10.1039/b922943d] [Citation(s) in RCA: 307] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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15 |
307 |
4
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Hoffman AS, Stayton PS, Bulmus V, Chen G, Chen J, Cheung C, Chilkoti A, Ding Z, Dong L, Fong R, Lackey CA, Long CJ, Miura M, Morris JE, Murthy N, Nabeshima Y, Park TG, Press OW, Shimoboji T, Shoemaker S, Yang HJ, Monji N, Nowinski RC, Cole CA, Priest JH, Harris JM, Nakamae K, Nishino T, Miyata T. Founder's Award, Society for Biomaterials. Sixth World Biomaterials Congress 2000, Kamuela, HI,May 15-20, 2000. Really smart bioconjugates of smart polymers and receptor proteins. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 2000; 52:577-86. [PMID: 11033539 DOI: 10.1002/1097-4636(20001215)52:4<577::aid-jbm1>3.0.co;2-5] [Citation(s) in RCA: 281] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Over the past 18 years we have been deeply involved with the synthesis and applications of stimuli-responsive polymer systems, especially polymer-biomolecule conjugates. This article summarizes our work with one of these conjugate systems, specifically polymer-protein conjugates. We include conjugates prepared by random polymer conjugation to lysine amino groups, and also those prepared by site-specific conjugation of the polymer to specific amino acid sites that are genetically engineered into the known amino acid sequence of the protein. We describe the preparation and properties of thermally sensitive random conjugates to enzymes and several affinity recognition proteins. We have also prepared site-specific conjugates to streptavidin with temperature-sensitive polymers, pH-sensitive polymers, and light-sensitive polymers. The preparation of these conjugates and their many fascinating applications are reviewed in this article.
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Review |
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281 |
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Gödecke A, Decking UK, Ding Z, Hirchenhain J, Bidmon HJ, Gödecke S, Schrader J. Coronary hemodynamics in endothelial NO synthase knockout mice. Circ Res 1998; 82:186-94. [PMID: 9468189 DOI: 10.1161/01.res.82.2.186] [Citation(s) in RCA: 206] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
For the specific analysis of endothelial NO synthase (eNOS) function in the coronary vasculature, we generated a mouse homozygous for a defective eNOS gene (eNOS-/-). Western blot as well as immunohistochemical staining revealed the absence of eNOS protein in eNOS-/- mice. Aortic endothelial cells derived from eNOS-/- mice displayed only background levels of NOx formation compared with wild-type (WT) cells (88 versus 1990 pmol NOx x h-1/mg protein-1). eNOS-/- mice were hypertensive (mean arterial pressure, 135 +/- 15 versus 107 +/- 8 mm Hg in WT) without the development of cardiac hypertrophy. Coronary hemodynamics, analyzed in Langendorff-perfused hearts, showed no differences either in basal coronary flow or in maximal and repayment flow of reactive hyperemia. Acute NOS inhibition with Nomega-nitro-L-arginine methyl ester (L-NAME) in WT hearts substantially reduced basal flow and reactive hyperemia. The coronary response to acetylcholine (ACh) (500 nmol/L) was biphasic: An initial vasoconstriction (flow, -35%) in WT hearts was followed by sustained vasodilation (+190%). L-NAME significantly reduced vasodilation in WT hearts (+125%) but did not alter the initial vasoconstriction. In eNOS-/- hearts, the initial vasoconstriction was augmented (-70%), whereas the ACh-induced vasodilation was not affected. Inhibition of cyclooxygenase with diclofenac converted the ACh-induced vasodilation into vasoconstriction (-49% decrease of basal flow). This effect was even more pronounced in eNOS-/- hearts (-71%). Our results demonstrate that (1) acute inhibition of eNOS reveals a role for NO in setting the basal coronary vascular tone as well as participation in reactive hyperemia and the response to ACh; (2) chronic inhibition of NO formation in eNOS-/- mutant mice induces no changes in basal coronary flow and reactive hyperemia, suggesting the activation of important compensatory mechanisms; and (3) prostaglandins are the main mediators of the ACh-induced vasodilation in both WT and eNOS-/- mice.
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Gödecke A, Flögel U, Zanger K, Ding Z, Hirchenhain J, Decking UK, Schrader J. Disruption of myoglobin in mice induces multiple compensatory mechanisms. Proc Natl Acad Sci U S A 1999; 96:10495-500. [PMID: 10468637 PMCID: PMC17917 DOI: 10.1073/pnas.96.18.10495] [Citation(s) in RCA: 196] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Myoglobin may serve a variety of functions in muscular oxygen supply, such as O(2) storage, facilitated O(2) diffusion, and myoglobin-mediated oxidative phosphorylation. We studied the functional consequences of a myoglobin deficiency on cardiac function by producing myoglobin-knockout (myo(-/-)) mice. To genetically inactivate the myoglobin gene, exon 2 encoding the heme binding site was deleted in embryonic stem cells via homologous recombination. Myo(-/-) mice are viable, fertile, and without any obvious signs of functional limitations. Hemoglobin concentrations were significantly elevated in myo(-/-) mice. Cardiac function and energetics were analyzed in isolated perfused hearts under resting conditions and during beta-adrenergic stimulation with dobutamine. Myo(-/-) hearts showed no alteration in contractile parameters either under basal conditions or after maximal beta-adrenergic stimulation (200 nM dobutamine). Tissue levels of ATP, phosphocreatine ((31)P-NMR), and myocardial O(2) consumption were not altered. However, coronary flow [6.4 +/- 1.3 ml.min(-1).g(-1) [wild-type (WT)] vs. 8.5 +/- 2.4 ml.min(-1).g(-1) [myo(-/-)] [and coronary reserve [17.1 +/- 2.1 (WT) vs. 20.8 +/- 1.1 (myo(-/-) ml. min(-1).g(-1) were significantly elevated in myo(-/-) hearts. Histological examination revealed that capillary density also was increased in myo(-/-) hearts [3,111 +/- 400 mm(-2) (WT) vs. 4,140 +/- 140 mm(-2) (Myo(-/-)]. These data demonstrate that disruption of myoglobin results in the activation of multiple compensatory mechanisms that steepen the pO(2) gradient and reduce the diffusion path length for O(2) between capillary and the mitochondria; this suggests that myoglobin normally is important for the delivery of oxygen.
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research-article |
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Ding Z, Fong RB, Long CJ, Stayton PS, Hoffman AS. Size-dependent control of the binding of biotinylated proteins to streptavidin using a polymer shield. Nature 2001; 411:59-62. [PMID: 11333975 DOI: 10.1038/35075028] [Citation(s) in RCA: 180] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Many medical and biotechnological processes rely on controlling and manipulating the molecular-recognition capabilities of proteins. This can be achieved using small molecules capable of competing for protein binding or by changing environmental parameters that affect protein structure and hence binding. An alternative is provided by stimuli-responsive polymers that change reversibly from a water-soluble expanded coil to a water-insoluble collapsed globule upon small changes in temperature, pH or light intensity: when attached to proteins in the vicinity of their binding sites, they reversibly block and release small ligands. Here we show how this approach can be extended to achieve size-selective binding of large, macromolecular ligands. We use the thermally responsive polymer poly(N,N-diethylacrylamide) (PDEAAm), and attach it to the protein streptavidin approximately 20 A from the binding site for biotinylated proteins. Below the lower critical solution temperature of PDEAAm, the polymer is in its extended state and acts as a 'shield' to block the binding of large biotinylated proteins; above this temperature, it collapses and exposes the binding site, thereby allowing binding. We find that the degree of shielding depends on both the size of the biotinylated protein and the size of PDEAAm, suggesting that 'smart' polymer shields could be tailored to achieve a wide range of size-dependent ligand discrimination for use in affinity separations, biosensors and diagnostics technologies.
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24 |
180 |
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Bulmus V, Ding Z, Long CJ, Stayton PS, Hoffman AS. Site-specific polymer-streptavidin bioconjugate for pH-controlled binding and triggered release of biotin. Bioconjug Chem 2000; 11:78-83. [PMID: 10639089 DOI: 10.1021/bc9901043] [Citation(s) in RCA: 178] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Low molecular weight copolymers of acrylic acid (AAc) and N-isopropylacrylamide (NIPAAm) have been synthesized with reactive OH groups at one end, using a chain transfer polymerization technique. The copolymer displays both pH and temperature sensitivity over a wide and useful range of pHs and temperatures, which permits both pH and temperature control of polymer conformation. This copolymer has been conjugated to a specific cysteine thiol site inserted by genetic engineering near the recognition site of streptavidin (SAv). In this paper, we demonstrate that this bioconjugate can provide pH control of biotin binding to and triggered release from the mutant SAv. These actions are relevant to affinity separations, biosensors, diagnostics, enzyme processes, and targeted delivery of drugs or chemical agents, labels, and other signals.
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178 |
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Liu S, Ding Z, Zhang C, Yang B, Liu Z. Gene knockdown by intro-thoracic injection of double-stranded RNA in the brown planthopper, Nilaparvata lugens. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2010; 40:666-671. [PMID: 20599616 DOI: 10.1016/j.ibmb.2010.06.007] [Citation(s) in RCA: 156] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2010] [Revised: 06/16/2010] [Accepted: 06/21/2010] [Indexed: 05/26/2023]
Abstract
RNA interference (RNAi) is a powerful strategy for gene function study in insects. Here, we described the development of a RNAi technique by microinjection of double-stranded RNA (dsRNA) in the brown planthopper Nilaparvata lugens. Based on the mortality and RNAi efficiency criteria, the conjunctive between prothorax and mesothorax was selected as the injection site and 50 nl as injection volume. Three genes with different expression patterns were selected to evaluate the RNAi efficiency. A comparable 40% decrease of gene expression was observed at the 4th day after injection for the ubiquitously expressed calreticulin and the gut specific cathepsin-B genes, but only 25% decrease at the 5th day for the central nervous system specific Nlbeta2 gene. Double injection could increase the RNAi efficiency, such as from 25% to 53% for Nlbeta2 gene. The gene knockdown technique developed in this study will be an essential post-genomic tool for further investigations in N. lugens.
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Evaluation Study |
15 |
156 |
10
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EL-Bourawi M, Khayet M, Ma R, Ding Z, Li Z, Zhang X. Application of vacuum membrane distillation for ammonia removal. J Memb Sci 2007. [DOI: 10.1016/j.memsci.2007.06.021] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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18 |
151 |
11
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Griffin L, Decker MJ, Hwang JY, Wang B, Kitchen K, Ding Z, Ivy JL. Functional electrical stimulation cycling improves body composition, metabolic and neural factors in persons with spinal cord injury. J Electromyogr Kinesiol 2008; 19:614-22. [PMID: 18440241 DOI: 10.1016/j.jelekin.2008.03.002] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2007] [Revised: 03/06/2008] [Accepted: 03/07/2008] [Indexed: 12/16/2022] Open
Abstract
Persons with spinal cord injury (SCI) are at a heightened risk of developing type II diabetes and cardiovascular disease. The purpose of this investigation was to conduct an analysis of metabolic, body composition, and neurological factors before and after 10 weeks of functional electrical stimulation (FES) cycling in persons with SCI. Eighteen individuals with SCI received FES cycling 2-3 times per week for 10 weeks. Body composition was analyzed by dual X-ray absorptiometry. The American Spinal Injury Association (ASIA) neurological classification of SCI test battery was used to assess motor and sensory function. An oral glucose tolerance (OGTT) and insulin-response test was performed to assess blood glucose control. Additional metabolic variables including plasma cholesterol (total-C, HDL-C, LDL-C), triglyceride, and inflammatory markers (IL-6, TNF-alpha, and CRP) were also measured. Total FES cycling power and work done increased with training. Lean muscle mass also increased, whereas, bone and adipose mass did not change. The ASIA motor and sensory scores for the lower extremity significantly increased with training. Blood glucose and insulin levels were lower following the OGTT after 10 weeks of training. Triglyceride levels did not change following training. However, levels of IL-6, TNF-alpha, and CRP were all significantly reduced.
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Research Support, Non-U.S. Gov't |
17 |
147 |
12
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Oh JK, Ding ZP, Gersh BJ, Bailey KR, Tajik AJ. Restrictive left ventricular diastolic filling identifies patients with heart failure after acute myocardial infarction. J Am Soc Echocardiogr 1992; 5:497-503. [PMID: 1389218 DOI: 10.1016/s0894-7317(14)80041-2] [Citation(s) in RCA: 123] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Left ventricular diastolic filling was characterized by transmitral pulsed-wave Doppler velocities in 62 patients with acute myocardial infarction, and diastolic filling variables were correlated with the presence of clinical heart failure. At the time of admission, 47 patients were free of heart failure and 15 patients were in Killip class II to IV. In the latter group of patients with heart failure, peak velocity of late filling wave caused by atrial contraction (A) was lower (0.48 versus 0.59 m/sec, p < 0.05), ratio of peak velocity of early rapid filling wave to peak velocity of late filling wave caused by atrial contraction (E/A) was higher (1.5 versus 1.1, p < 0.01), and deceleration time (136 versus 196 msec, p = 0.0001) was shorter when compared with the patients not in heart failure after acute myocardial infarction. Multivariate analysis showed that the deceleration time was a powerful independent predictor of presence of heart failure after controlling for systolic functional variables. Therefore, diastolic filling variables can complement systolic functional variables in the identification of the patients with postinfarction left ventricular failure.
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33 |
123 |
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Yang X, Chernenko G, Hao Y, Ding Z, Pater MM, Pater A, Tang SC. Human BAG-1/RAP46 protein is generated as four isoforms by alternative translation initiation and overexpressed in cancer cells. Oncogene 1998; 17:981-9. [PMID: 9747877 DOI: 10.1038/sj.onc.1202032] [Citation(s) in RCA: 113] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Previously, a Bcl-2-interacting protein, BAG-1, was cloned from mouse cells and was shown to interact with several other proteins and to be important for inhibition of apoptosis. Human BAG-1 (hBAG-1) cDNA, recently isolated by us and two other groups, has been shown to be identical to a hormone receptor-binding protein, RAP46. However, different molecular masses of hBAG-1 protein products were noted by these three groups. Here we demonstrated that hBAG-1 protein was expressed as four isoforms, designated p50, p46, p33 and p29, with apparent molecular masses of 50 kDa, 46 kDa, 33 kDa and 29 kDa, respectively. Deletion, site-directed mutagenesis and in vitro transcription/translation analysis showed that the four protein products of hBAG-1 were expressed by alternative initiation from four different start codons through a leaky scanning mechanism. Furthermore, we demonstrated that the distinct forms of hBAG-1 have different subcellular localizations, suggesting that they may have distinct functions in the cells. Characterization of hBAG-1 RNA and protein also showed that hBAG-1 was overexpressed in human cervical, breast and lung cancer cell lines. Taken together, these data clarify the conflicting observations reported in the literature and suggest that hBAG-1 is expressed as four forms of protein products, which may play a differential role in apoptosis and oncogenesis of human cells.
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113 |
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Ding Z, Wen Y, Yang B, Zhang Y, Liu S, Liu Z, Han Z. Biochemical mechanisms of imidacloprid resistance in Nilaparvata lugens: over-expression of cytochrome P450 CYP6AY1. INSECT BIOCHEMISTRY AND MOLECULAR BIOLOGY 2013; 43:1021-1027. [PMID: 23994173 DOI: 10.1016/j.ibmb.2013.08.005] [Citation(s) in RCA: 112] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2011] [Revised: 08/13/2013] [Accepted: 08/15/2013] [Indexed: 06/02/2023]
Abstract
Imidacloprid is a key insecticide extensively used for control of Nilaparvata lugens, and its resistance had been reported both in the laboratory selected strains and field populations. A target site mutation Y151S in two nicotinic acetylcholine receptor subunits and enhanced oxidative detoxification have been identified in the laboratory resistant strain, contributing importantly to imidacloprid resistance in N. lugens. To date, however, imidacloprid resistance in field population is primarily attributable to enhanced oxidative detoxification by over-expressed P450 monooxygenases. A resistant strain (Res), originally collected from a field population and continuously selected in laboratory with imidacloprid for more than 40 generations, had 180.8-fold resistance to imidacloprid, compared to a susceptible strain (Sus). Expression of different putative P450 genes at mRNA levels was detected and compared between Res and Sus strains, and six genes were found expressed significantly higher in Res strain than in Sus strain. CYP6AY1 was found to be the most different expressed P450 gene and its mRNA level in Res strain was 17.9 times of that in Sus strain. By expressing in E. coli cells, CYP6AY1 was found to metabolize imidacloprid efficiently with initial velocity calculated of 0.851 ± 0.073 pmol/min/pmol P450. When CYP6AY1 mRNA levels in Res strain was reduced by RNA interference, imidacloprid susceptibility was recovered. In four field populations with different resistance levels, high levels of CYP6AY1 transcript were also found. In vitro and in vivo studies provided evidences that the over-expression of CYP6AY1 was one of the key factors contributing to imidacloprid resistance in the laboratory selected strain Res, which might also be the important mechanism for imidacloprid resistance in field populations, when the target site mutation was not prevalent at present.
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12 |
112 |
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Ding Z, Zhu HY, Lu GQ, Greenfield PF. Photocatalytic Properties of Titania Pillared Clays by Different Drying Methods. J Colloid Interface Sci 1999; 209:193-199. [PMID: 9878152 DOI: 10.1006/jcis.1998.5857] [Citation(s) in RCA: 111] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Photocatalysts based on titania pillared clays (TiO2 PILCs) have been prepared through a sol-gel method. Different drying methods, air drying (AD), air drying after ethanol extraction (EAD), and supercritical drying (SCD) have been employed and found to have significant effects on the photocatalytic efficiency of the resultant catalysts for the oxidation of phenol in water. Titania pillared clay (TiO2 PILC) obtained by SCD has the highest external and micropore surface area, largest amount and smallest crystallite size of anatase, and exhibited the highest photocatalytic activity. Furthermore, silica titania pillared clay (SiO2-TiO2 PILC) after SCD, titania coated TiO2 PILC (SCD) and SiO2-TiO2 PILC (SCD) were synthesized to study the key factors controlling the photocatalytic activity. It is concluded that the dispersion of nanometer-sized anatase on the surface of the PILC particles and the suspensibility of the particles are the most important factors for high photocatalytic efficiency. Copyright 1999 Academic Press.
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111 |
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Ding Z, Chen G, Hoffman AS. Synthesis and purification of thermally sensitive oligomer-enzyme conjugates of poly(N-isopropylacrylamide)-trypsin. Bioconjug Chem 1996; 7:121-6. [PMID: 8741999 DOI: 10.1021/bc950087r] [Citation(s) in RCA: 100] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
Using chain-transfer polymerization, we have synthesized oligomers of poly(N-isopropylacrylamide) [poly(NIPAAm)] with one carboxyl group at the end of each oligomer chain. The lower critical solution temperature (LCST) of the oligomers is very close to that of homo-poly(NIPAAm) lacking the end carboxyl group. The carboxyl groups were activated in methylene chloride using N,N'-dicyclohexyl-carbodiimide (DCC) and N-hydroxysuccinimide (NHS). A conjugate of trypsin with the preactivated oligomer has been prepared. We studied the effect of oligomer to enzyme (O/E) ratio in the feed on the O/E ratio of the conjugate (the average number of oligomer chains conjugated to one trypsin molecule), assuming that only the primary amino groups of lysine residues and the amino terminal of trypsin would react. The O/E ratio of the conjugate was estimated by determination of the remaining primary amine groups on the trypsin molecule. More than 95% of the conjugate can be recovered by thermally induced precipitation.
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Comparative Study |
29 |
100 |
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Ding Z, Long CJ, Hayashi Y, Bulmus EV, Hoffman AS, Stayton PS. Temperature control of biotin binding and release with A streptavidin-poly(N-isopropylacrylamide) site-specific conjugate. Bioconjug Chem 1999; 10:395-400. [PMID: 10346869 DOI: 10.1021/bc980108s] [Citation(s) in RCA: 97] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The many laboratory and diagnostic applications utilizing streptavidin as a molecular adaptor rely on its high affinity and essentially irreversible interaction with biotin. However, there are many situations where recovery of the biotinylated molecules is desirable. We have previously shown that poly(N-isopropylacrylamide) (PNIPAAm), a temperature-sensitive polymer, can reversibly block biotin association as the polymer's conformation changes at its lower critical solution temperature (LCST). Here, we have constructed a streptavidin-PNIPAAm conjugate which is able to bind biotin at room temperature or lower and release bound biotin at 37 degrees C. The conjugate can repeatedly bind and release biotin as temperature is cycled through the LCST. A genetically engineered streptavidin mutant, E116C, which has only one cysteine residue, was conjugated site specifically via the sulfhydryl groups with a PNIPAAm that has pendent sulfhydryl-reactive vinyl sulfone groups. The conjugation site is near the tryptophan 120 residue, which forms a van der Waals contact with biotin that is important in generating the large binding free energy. The temperature-induced conformational change of the polymer at position 116 may lead to structural changes in the region of tryptophan 120 that are responsible for the reversible binding between biotin and the conjugated streptavidin.
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97 |
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Zheng H, Ying H, Yan H, Kimmelman AC, Hiller DJ, Chen AJ, Perry SR, Tonon G, Chu GC, Ding Z, Stommel JM, Dunn KL, Wiedemeyer R, You MJ, Brennan C, Wang YA, Ligon KL, Wong WH, Chin L, dePinho RA. Pten and p53 converge on c-Myc to control differentiation, self-renewal, and transformation of normal and neoplastic stem cells in glioblastoma. COLD SPRING HARBOR SYMPOSIA ON QUANTITATIVE BIOLOGY 2009; 73:427-37. [PMID: 19150964 DOI: 10.1101/sqb.2008.73.047] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Glioblastoma (GBM) is a highly lethal primary brain cancer with hallmark features of diffuse invasion, intense apoptosis resistance and florid necrosis, robust angiogenesis, and an immature profile with developmental plasticity. In the course of assessing the developmental consequences of central nervous system (CNS)-specific deletion of p53 and Pten, we observed a penetrant acute-onset malignant glioma phenotype with striking clinical, pathological, and molecular resemblance to primary GBM in humans. This primary, as opposed to secondary, GBM presentation in the mouse prompted genetic analysis of human primary GBM samples that revealed combined p53 and Pten mutations as the most common tumor suppressor defects in primary GBM. On the mechanistic level, the "multiforme" histopathological presentation and immature differentiation marker profile of the murine tumors motivated transcriptomic promoter-binding element and functional studies of neural stem cells (NSCs), which revealed that dual, but not singular, inactivation of p53 and Pten promotes cellular c-Myc activation. This increased c-Myc activity is associated not only with impaired differentiation, enhanced self-renewal capacity of NSCs, and tumor-initiating cells (TICs), but also with maintenance of TIC tumorigenic potential. Together, these murine studies have provided a highly faithful model of primary GBM, revealed a common tumor suppressor mutational pattern in human disease, and established c-Myc as a key component of p53 and Pten cooperative actions in the regulation of normal and malignant stem/progenitor cell differentiation, self-renewal, and tumorigenic potential.
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Research Support, Non-U.S. Gov't |
16 |
97 |
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Tang W, Ding Z, Zhou ZQ, Wang YZ, Guo LY. Phylogenetic and Pathogenic Analyses Show That the Causal Agent of Apple Ring Rot in China Is Botryosphaeria dothidea. PLANT DISEASE 2012; 96:486-496. [PMID: 30727432 DOI: 10.1094/pdis-08-11-0635] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Apple ring rot and Botryosphaeria canker are severe diseases affecting apple production in China, but there is confusion regarding which pathogens cause these diseases and their similarity to other diseases, such as white rot of apple, and ring rot and Botryosphaeria canker of pear. In this study, the pathogen of apple ring rot in China was compared with the pathogen of apple ring rot in Japan and Korea, the pathogen of Botryosphaeria canker of apple and pear in China, the pathogen of pear ring rot in China, and the pathogen of white rot of apple in the United States. Comparisons were based on morphology, pathogenicity on branches and fruit, and sequences of rDNA in the internal transcribed spacer region and of the β-tubulin and actin genes. Results showed that the causal agent of apple ring rot and Botryosphaeria canker of apple in China was Botryosphaeria dothidea, which has also been reported to be the pathogen of apple ring rot in Korea and Japan. Pathogenicity tests showed that B. dothidea infection on apple and pear branches may induce wart or canker symptoms depending on the conditions. These results are consistent with the hypothesis that the same pathogen causes the wart symptom of apple ring rot and the Botryosphaeria canker symptom on apple branches in China. The results also suggest that apple ring rot and white rot are the same disease and are caused by B. dothidea. Finally, B. dothidea isolates from pear and other fruit or forest trees may serve as inoculum for apple ring rot.
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13 |
96 |
20
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Ding Z, Chen G, Hoffman AS. Unusual properties of thermally sensitive oligomer-enzyme conjugates of poly(N-isopropylacrylamide)-trypsin. JOURNAL OF BIOMEDICAL MATERIALS RESEARCH 1998; 39:498-505. [PMID: 9468062 DOI: 10.1002/(sici)1097-4636(19980305)39:3<498::aid-jbm22>3.0.co;2-5] [Citation(s) in RCA: 95] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Reversible soluble-insoluble oligomer-enzyme conjugates have been prepared by conjugating a thermally sensitive oligomer, poly(N-isopropylacrylamide) [poly(NIPAAm)] to trypsin. The conjugates can catalyze enzymatic reactions in solution and then may be separated from the solution by thermal precipitation. One special feature of the conjugates is that every poly(NIPAAm) chain has only one end attachment to the enzyme, so that the loss of enzymatic activity due to steric hindrance should be minimized. Conjugates with various numbers of oligomer chains per trypsin molecule were prepared. Surprisingly, the conjugates increased in enzymatic activity with increasing oligomer conjugation to the native trypsin. The trypsin active sites in the conjugates were accessible to large molecules, such as soybean trypsin inhibitor (MW = 21,500). The enzyme conjugates were more stable than native trypsin, both in solution and in the precipitated phase. On the other hand, the conjugates lost enzymatic activity faster than native trypsin when the temperature was repeatedly cycled through the lower critical solution temperature (LCST) of the poly(NIPAAm). The recovery of the conjugates by thermal precipitation in each cycle was over 95% even after 14 cycles through the LCST.
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LaBella VP, Bullock DW, Ding Z, Emery C, Venkatesan A, Oliver WF, Salamo GJ, Thibado PM, Mortazavi M. Spatially Resolved Spin-Injection Probability for Gallium Arsenide. Science 2001; 292:1518-21. [PMID: 11375485 DOI: 10.1126/science.292.5521.1518] [Citation(s) in RCA: 87] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
We report a large spin-polarized current injection from a ferromagnetic metal into a nonferromagnetic semiconductor, at a temperature of 100 Kelvin. The modification of the spin-injection process by a nanoscale step edge was observed. On flat gallium arsenide [GaAs(110)] terraces, the injection efficiency was 92%, whereas in a 10-nanometer-wide region around a [111]-oriented step the injection efficiency is reduced by a factor of 6. Alternatively, the spin-relaxation lifetime was reduced by a factor of 12. This reduction is associated with the metallic nature of the step edge. This study advances the realization of using both the charge and spin of the electron in future semiconductor devices.
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Eapen M, Zald DH, Gatenby JC, Ding Z, Gore JC. Using high-resolution MR imaging at 7T to evaluate the anatomy of the midbrain dopaminergic system. AJNR Am J Neuroradiol 2010; 32:688-94. [PMID: 21183619 DOI: 10.3174/ajnr.a2355] [Citation(s) in RCA: 84] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
BACKGROUND AND PURPOSE Dysfunction of DA neurotransmission from the SN and VTA has been implicated in neuropsychiatric diseases, including Parkinson disease and schizophrenia. Unfortunately, these midbrain DA structures are difficult to define on clinical MR imaging. To more precisely evaluate the anatomic architecture of the DA midbrain, we scanned healthy participants with a 7T MR imaging system. Here we contrast the performance of high-resolution T2- and T2*-weighted GRASE and FFE MR imaging scans at 7T. MATERIALS AND METHODS Ten healthy participants were scanned by using GRASE and FFE sequences. CNRs were calculated among the SN, VTA, and RN, and their volumes were estimated by using a segmentation algorithm. RESULTS Both GRASE and FFE scans revealed visible contrast between midbrain DA regions. The GRASE scan showed higher CNRs compared with the FFE scan. The T2* contrast of the FFE scan further delineated substructures and microvasculature within the midbrain SN and RN. Segmentation and volume estimation of the midbrain SN, RN, and VTA showed individual differences in the size and volume of these structures across participants. CONCLUSIONS Both GRASE and FFE provide sufficient CNR to evaluate the anatomy of the midbrain DA system. The FFE in particular reveals vascular details and substructure information within the midbrain regions that could be useful for examining structural changes in midbrain pathologies.
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Ma R, Wang X, Lu C, Li C, Cheng Y, Ding G, Liu L, Ding Z. Dexamethasone attenuated bupivacaine-induced neuron injury in vitro through a threonine–serine protein kinase B-dependent mechanism. Neuroscience 2010; 167:329-42. [DOI: 10.1016/j.neuroscience.2009.12.049] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2009] [Revised: 12/18/2009] [Accepted: 12/22/2009] [Indexed: 01/24/2023]
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Ding Z, Verbaan F, Bivas-Benita M, Bungener L, Huckriede A, van den Berg D, Kersten G, Bouwstra J. Microneedle arrays for the transcutaneous immunization of diphtheria and influenza in BALB/c mice. J Control Release 2009; 136:71-8. [DOI: 10.1016/j.jconrel.2009.01.025] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2008] [Revised: 01/23/2009] [Accepted: 01/28/2009] [Indexed: 10/21/2022]
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Fong RB, Ding Z, Long CJ, Hoffman AS, Stayton PS. Thermoprecipitation of streptavidin via oligonucleotide-mediated self-assembly with poly(N-isopropylacrylamide). Bioconjug Chem 1999; 10:720-5. [PMID: 10502336 DOI: 10.1021/bc980151f] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A versatile strategy has been developed for selectively and sequentially isolating targets in a liquid-phase affinity separation environment. The strategy uses a recently developed approach for joining together molecules in linkages that are defined by the complementary pairing of oligonucleotides conjugated to the different molecules [Niemeyer, C. M., Sano, T., Smith, C. L., and Cantor, C. R. (1994) Nucleic Acids Res. 22, 5530-9]. In the work presented here, streptavidin was noncovalently coupled with the temperature-responsive poly(N-isopropylacrylamide) [poly(NIPAAM)] through the sequence-specific hybridization of oligonucleotides conjugated to the protein and polymer. A 20-mer oligonucleotide was covalently linked through a heterobifunctional linker to a genetically engineered streptavidin variant that contained a unique cysteine residue at the solvent-accessible site Glu 116. The complementary DNA sequence was conjugated to the end of a linear ester-activated poly(NIPAAM). The two conjugates were allowed to self-assemble in solution via hybridization of their complementary DNA sequences. The streptavidin-poly(NIPAAM) complex could be used to affinity-precipitate radiolabeled biotin or biotinylated alkaline phosphatase above 32 degrees C through the thermally induced phase separation activity of the poly(NIPAAM). The streptavidin-oligo species could then be reversibly separated from the precipitated polymer-oligo conjugate and recycled by lowering the salt concentration, which results in denaturation of the short double-stranded DNA connection. The use of oligonucleotides to couple polymer to streptavidin allows for selective precipitation of different polymers and streptavidin complexes based on the sequence-specific hybridization of their oligonucleotide appendages.
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