The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Bradley D. Olsen - One of the best experts on this subject based on the ideXlab platform.
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secondary structure drives self assembly in weakly segregated globular protein rod block copolymers
Polymer Chemistry, 2020Co-Authors: Kai Sheng, Hua Lu, Bradley D. OlsenAbstract:Protein–polymer Bioconjugates represent a class of materials that integrate protein functionality with polymer material properties and block copolymer self-assembly. To investigate the effect of polymer block secondary structure and chirality on self-assembly of globular protein–helix diblock copolymers, four types of Bioconjugates consisting of a poly(amino acid) and enhanced green fluorescent protein (eGFP) were synthesized and compared: two homochiral, α-helix-forming Bioconjugates incorporating either L- or D-type poly(amino acids), a 1 : 1 blend of the L- and D-type Bioconjugates, and a Bioconjugate incorporating structureless, achiral poly(amino acids). Poly(amino acids) (PAAs) were synthesized via N-carboxy anhydride (NCA) polymerization, and PAAs were conjugated to eGFP via native chemical ligation. All Bioconjugates with a helical block self-assembled into lamellae at all concentrations measured (20 to 60 wt%). In contrast, the random copolymer of L- and D-type monomers did not self-assemble at any concentration or temperature. This was shown to be an effect of a non-repulsive interaction between the flexible PAA and the eGFP blocks, which is strong enough to affect the protonation state of the eGFP chromophore in water. Therefore, secondary structure of the polymer block can modulate the effective segregation strength between blocks and drive self-assembly even in systems with non-repulsive blocks.
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effect of polymer chemistry on globular protein polymer block copolymer self assembly
Polymer Chemistry, 2014Co-Authors: Dongsook Chang, Shengchang Tang, Bradley D. OlsenAbstract:Bioconjugates of the model red fluorescent protein mCherry and synthetic polymer blocks with different hydrogen bonding functionalities show that the chemistry of the polymer block has a large effect on both ordering transitions and the type of nanostructures formed during Bioconjugate self-assembly. The phase behaviours of mCherry-b-poly(hydroxypropyl acrylate) (PHPA) and mCherry-b-poly(oligoethylene glycol acrylate) (POEGA) in concentrated aqueous solution show that changes in polymer chemistry result in increase in the order–disorder transition concentrations (CODTs) by approximately 10–15 wt% compared to a previously studied globular protein–polymer block copolymer, mCherry-b-poly(N-isopropylacrylamide) (PNIPAM). The CODTs are always minimized for symmetric Bioconjugates, consistent with the importance of protein–polymer interactions in self-assembly. Both mCherry-b-PHPA and mCherry-b-POEGA also form phases that have not previously been observed in other globular protein–polymer conjugates: mCherry-b-PHPA forms a cubic phase that can be indexed to Iad and mCherry-b-POEGA displays coexistence of lamellae and a cubic Iad structure over a narrow range of concentration and temperature. Several common behaviours are also revealed by comparison of different polymer blocks. With increasing concentration and temperature, ordered phases always appear in the order lamellar, cubic/PL, and hexagonal, although not all phases are observed in all materials. High concentration solutions (near 80 wt%) also undergo a re-entrant order–disorder transition to form nematic liquid crystalline phases, regardless of the polymer block chemistry.
James F Rusling - One of the best experts on this subject based on the ideXlab platform.
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ultrasensitive immunosensor for cancer biomarker proteins using gold nanoparticle film electrodes and multienzyme particle amplification
ACS Nano, 2009Co-Authors: Vigneshwaran Mani, Vyomesh Patel, Silvio J Gutkind, Bhaskara V Chikkaveeraiah, James F RuslingAbstract:A densely packed gold nanoparticle platform combined with a multiple-enzyme labeled detection antibody-magnetic bead Bioconjugate was used as the basis for an ultrasensitive electrochemical immunosensor to detect cancer biomarkers in serum. Sensitivity was greatly amplified by synthesizing magnetic Bioconjugates particles containing 7500 horseradish peroxidase (HRP) labels along with detection antibodies (Ab2) attached to activated carboxyl groups on 1 μm diameter magnetic beads. These sensors had sensitivity of 31.5 μA mL ng−1 and detection limit (DL) of 0.5 pg mL−1 for prostate specific antigen (PSA) in 10 μL of undiluted serum. This represents an ultralow mass DL of 5 fg PSA, 8-fold better than a previously reported carbon nanotube (CNT) forest immunosensor featuring multiple labels on carbon nanotubes, and near or below the normal serum levels of most cancer biomarkers. Measurements of PSA in cell lysates and human serum of cancer patients gave excellent correlations with standard ELISA assays. These ...
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targeted killing of cancer cells in vivo and in vitro with egf directed carbon nanotube based drug delivery
ACS Nano, 2009Co-Authors: Ashwin Bhirde, Vyomesh Patel, Julie Gavard, Guofeng Zhang, Alioscka A Sousa, Andrius Masedunskas, Richard D Leapman, Roberto Weigert, Silvio J Gutkind, James F RuslingAbstract:Carbon nanotube-based drug delivery holds great promise for cancer therapy. Herein we report the first targeted, in vivo killing of cancer cells using a drug-single wall carbon nanotube (SWNT) Bioconjugate, and demonstrate efficacy superior to nontargeted Bioconjugates. First line anticancer agent cisplatin and epidermal growth factor (EGF) were attached to SWNTs to specifically target squamous cancer, and the nontargeted control was SWNT-cisplatin without EGF. Initial in vitro imaging studies with head and neck squamous carcinoma cells (HNSCC) overexpressing EGF receptors (EGFR) using Qdot luminescence and confocal microscopy showed that SWNT-Qdot-EGF Bioconjugates internalized rapidly into the cancer cells. Limited uptake occurred for control cells without EGF, and uptake was blocked by siRNA knockdown of EGFR in cancer cells, revealing the importance of EGF-EGFR binding. Three color, two-photon intravital video imaging in vivo showed that SWNT-Qdot-EGF injected into live mice was selectively taken up b...
Murali Sastry - One of the best experts on this subject based on the ideXlab platform.
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spider silk as an active scaffold in the assembly of gold nanoparticles and application of the gold silk Bioconjugate in vapor sensing
Small, 2007Co-Authors: Amit Kumar Singh, Shantesh Hede, Murali SastryAbstract:Spider silk is being viewed with interest by materials scientists due to its excellent resilience and mechanical properties. In this paper we show that spider silk is an excellent scaffold for the one-step synthesis and assembly of gold nanoparticles. Formation of a gold nanoparticle–spider-silk Bioconjugate material is accomplished by simple reaction of the fibers with aqueous chloroauric acid. The gold nanoparticles thus formed are strongly bound to the spider-silk fiber surface enabling study of the electrical properties of the nanoBioconjugate. Using the well-known contraction/expansion behavior of the fibers in solvents of varying polarity, we show that exposure of the gold nanoparticle–spider silk Bioconjugate to vapors of methanol and chloroform leads to changes in electrical transport through the nanoparticles and thus, the possibility of developing a vapor sensor. The Bioconjugate shows excellent response time and cycling efficiency to methanol vapors. The activation energy of electron transport from one gold nanoparticle to another in the nanobiocojugate was determined from temperature-dependent electron-transport measurements to be approximately 1.7 eV.
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pepsin gold colloid conjugates preparation characterization and enzymatic activity
Langmuir, 2001Co-Authors: Anand Gole, Chandravanu Dash, Vidya Ramakrishnan, S R Sainkar, Anandrao B. Mandale, Murali SastryAbstract:Pepsin−colloidal gold conjugates were prepared by a simple protein-friendly process and the enzymatic activity of the Bioconjugates is reported. The pepsin−gold conjugates are obtained by mixing colloidal gold and protein solutions at pH = 3 and, thereafter, centrifugation, washing, and redispersion of the pepsin−gold conjugate material in water. The Bioconjugates in solution were characterized by UV−vis spectroscopy, fluorescence spectroscopy, and biocatalytic activity measurements while films of the Bioconjugate material obtained by solvent evaporation on suitable substrates were further analyzed by scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), transmission electron spectroscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). While TEM and SEM measurements showed aggregates of the enzyme/colloidal gold conjugates, the intactness of secondary and tertiary structures of the enzyme, as determined by FTIR and fluorescence s...
Roger M Leblanc - One of the best experts on this subject based on the ideXlab platform.
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cdse zns quantum dots and organophosphorus hydrolase Bioconjugate as biosensors for detection of paraoxon
Journal of Physical Chemistry B, 2005Co-Authors: Jiayin Zheng, Vipin K Rastogi, Tu Chen Cheng, Joseph J Defrank, Roger M LeblancAbstract:In this paper, we first report a novel biosensor for the detection of paraoxon based on (CdSe)ZnS core-shell quantum dots (QDs) and an organophosphorus hydrolase (OPH) Bioconjugate. The OPH was coupled to (CdSe)ZnS core-shell QDs through electrostatic interaction between negatively charged QDs surfaces and the positively charged protein side chain and ending groups (-NH2). Circular dichroism (CD) spectroscopy showed no significant change in the secondary structure of OPH after the bioconjugation, which indicates that the activity of OPH was preserved. Detectable secondary structure changes were observed by CD spectroscopy when the OPH/QDs Bioconjugate was exposed to organophosphorus compounds such as paraoxon. Photoluminescence (PL) spectroscopic study showed that the PL intensity of the OPH/QDs Bioconjugate was quenched in the presence of paraoxon. The overall quenching percentage as a function of paraoxon concentration matched very well with the Michaelis-Menten equation. This result indicated that the quenching of PL intensity was caused by the conformational change in the enzyme, which is confirmed by CD measurements. The detection limit of paraoxon concentration using OPH/QDs Bioconjugate was about 10(-8) M. Although increasing the OPH molar ratio in the Bioconjugates will slightly increase the sensitivity of biosensor, no further increase of sensitivity was achieved when the molar ratio of OPH to QDs was greater than 20 because the surface of QDs was saturated by OPH. These properties make the OPH/QDs Bioconjugate a promising biosensor for the detection of organophosphorus compounds.
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cdse zns quantum dots and organophosphorus hydrolase Bioconjugate as biosensors for detection of paraoxon
Journal of Physical Chemistry B, 2005Co-Authors: Jiayin Zheng, Vipin K Rastogi, Tu Chen Cheng, Joseph J Defrank, Roger M LeblancAbstract:In this paper, we first report a novel biosensor for the detection of paraoxon based on (CdSe)ZnS core−shell quantum dots (QDs) and an organophosphorus hydrolase (OPH) Bioconjugate. The OPH was coupled to (CdSe)ZnS core−shell QDs through electrostatic interaction between negatively charged QDs surfaces and the positively charged protein side chain and ending groups (−NH2). Circular dichroism (CD) spectroscopy showed no significant change in the secondary structure of OPH after the bioconjugation, which indicates that the activity of OPH was preserved. Detectable secondary structure changes were observed by CD spectroscopy when the OPH/QDs Bioconjugate was exposed to organophosphorus compounds such as paraoxon. Photoluminescence (PL) spectroscopic study showed that the PL intensity of the OPH/QDs Bioconjugate was quenched in the presence of paraoxon. The overall quenching percentage as a function of paraoxon concentration matched very well with the Michaelis−Menten equation. This result indicated that the ...
Yitao Long - One of the best experts on this subject based on the ideXlab platform.
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correction corrigendum ubiquinone quantum dot Bioconjugates for in vitro and intracellular complex i sensing
Scientific Reports, 2013Co-Authors: Zhen Gu, Jian Wang, Tony D James, Yitao LongAbstract:Quantum dots (QDs) have attracted increasing interest in bioimaging and sensing. Here, we report a biosensor of complex I using ubiquinone-terminated disulphides with different alkyl spacers (QnNS, n = 2, 5 and 10) as surface-capping ligands to functionalise CdSe/ZnS QDs. The enhancement or quenching of the QD Bioconjugates fluorescence changes as a function of the redox state of QnNS, since QDs are highly sensitive to the electron-transfer processes. The Bioconjugated QnNS-QDs emission could be modulated by complex I in the presence of NADH, which simulates an electron-transfer system part of the mitochondrial respiratory chain, providing an in vitro and intracellular complex I sensor. Epidemiological studies suggest that Parkinson's patients have the impaired activity of complex I in the electron-transfer chain of mitochondria. We have demonstrated that the QnNS-QDs system could aid in early stage Parkinson's disease diagnosis and progression monitoring by following different complex I levels in SH-SY5Y cells.
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ubiquinone quantum dot Bioconjugates for in vitro and intracellular complex i sensing
Scientific Reports, 2013Co-Authors: Lixia Qin, Jian Wang, Tony D James, Feng Tao Liu, Zhi Gang Pan, Yitao LongAbstract:Quantum dots (QDs) have attracted increasing interest in bioimaging and sensing. Here, we report a biosensor of complex I using ubiquinone-terminated disulphides with different alkyl spacers (QnNS, n = 2, 5 and 10) as surface-capping ligands to functionalise CdSe/ZnS QDs. The enhancement or quenching of the QD Bioconjugates fluorescence changes as a function of the redox state of QnNS, since QDs are highly sensitive to the electron-transfer processes. The Bioconjugated QnNS-QDs emission could be modulated by complex I in the presence of NADH, which simulates an electron-transfer system part of the mitochondrial respiratory chain, providing an in vitro and intracellular complex I sensor. Epidemiological studies suggest that Parkinson's patients have the impaired activity of complex I in the electron-transfer chain of mitochondria. We have demonstrated that the QnNS-QDs system could aid in early stage Parkinson's disease diagnosis and progression monitoring by following different complex I levels in SH-SY5Y cells.