Biomedical subjects

Dafu Cui

Publications and source records attributed to Dafu Cui.

9 recordsLinked to original sources

PubMed2006

Mice with genetically altered GABA transporter subtype I (GAT1) expression show altered behavioral responses to ethanol.

It is widely accepted that the GABAergic system plays an important role in the action of ethanol in vivo. GABA transporter subtype 1 (GAT1) constructs high affinity reuptake sites in the CNS and regulates GABAergic transmissions. In this study, mice lacking the GAT1 were developed by homologous recombination. Both hetero- and homozygous GAT1 mutant mice were tested for ethanol, saccharin or quinine consumption, ethanol-conditioned place preference, ethanol-conditioned taste aversion, ethanol-simulated motor activity, and ethanol-induced sedation/hypnosis. The GAT1(-/-) mice showed decreased ethanol aversion and ethanol reward, and insensitivity to both the sedative/hypnotic and the motor stimulant effects of ethanol, along with increased avoidance of quinine preference and consumption. GAT1(+/-) mice showed significantly increased consumption of ethanol and saccharin, however, enhanced the rewarding and preference effect of ethanol, increased avoidance of quinine, and higher sensitivity to the motor stimulant effect of ethanol. These results demonstrate that GAT1, perhaps in a bi-directional way, modulates some behavioral effects of ethanol. The GAT1 mutant mice provided us a very useful model to investigate the mechanisms of ethanol action in vivo.

Analgesics, Non-Narcotic↗

PubMed2006

Development of peptidic dopamine transporter inhibitors via aromatic modification-mediated conformational restriction.

The dopamine transporter plays an important role in the molecular mechanism of cocaine dependence. It is suggested that inhibitors of the dopamine transporter would have strong therapeutic potential. Here we report that aromatic modification can constrain a linear peptide into the beta-turn conformation, which is preferred by the dopamine transporter. On the basis of this finding, a novel selective and competitive peptidic inhibitor of the dopamine transporter was developed. The peptide binds to the dopamine- and cocaine-binding site of the dopamine transporter and has behavioral effects different from those of cocaine in mice.

Animals↗

PubMed2006

High-power and high-quality, green-beam generation by employing a thermally near-unstable resonator design.

We have obtained green-beam quality of M2 = 6.2 at an average output power of 120 W by intracavity frequency doubling of a diode-side-pumped, Q-switched Nd:YAG rod laser with a repetition rate of 10 kHz and an optical-to-optical conversion efficiency of 15.2%. To achieve high-beam quality at high average power, the laser employs a thermally near-unstable resonator design with two-rod birefringence compensation in an L-shaped flat-flat cavity. The output power fluctuation of the green laser remains less than 0.9% in 4 h.

Journal Article↗

PubMed2006

A rigid poly(dimethylsiloxane) sandwich electrophoresis microchip based on thin-casting method.

We present a novel concept of glass/poly(dimethylsiloxane) (PDMS)/glass sandwich microchip and developed a thin-casting method for fabrication. Unlike the previously reported casting method for fabricating PDMS microchip, several drops of PDMS prepolymer were first added on the silanizing SU-8 master, then another glass plate was placed over the prepolymer as a cover plate, and formed a glass plate/PDMS prepolymer/SU-8 master sandwich mode. In order to form a thin PDMS membrane, a weight was placed on the glass plate. After the whole sandwich mode was cured at 80 degrees C for 30 min, the SU-8 master was easily peeled and the master microstructures were completely transferred to the PDMS membrane which was tightly stuck to the glass plate. The microchip was subsequently assembled by reversible sealing with the glass cover plate. We found that this PDMS sandwich microchip using the thin-casting method could withstand internal pressures of >150 kPa, more than 5 times higher than that of the PDMS hybrid microchip with reversible sealing. In addition, it shows an excellent heat-dissipating property and provides a user-friendly rigid interface just like a glass microchip, which facilitates manipulation of the microchip and fix tubing. As an application, PDMS sandwich microchips were tested in the capillary electrophoresis separation of fluorescein isothiocyanate-labeled amino acids.

Amino Acids↗

PubMed2006

Template-assisted rational design of peptide inhibitors of furin using the lysine fragment of the mung bean trypsin inhibitor.

Highly active, small-molecule furin inhibitors are attractive drug candidates to fend off bacterial exotoxins and viral infection. Based on the 22-residue, active Lys fragment of the mung bean trypsin inhibitor, a series of furin inhibitors were designed and synthesized, and their inhibitory activity towards furin and kexin was evaluated using enzyme kinetic analysis. The most potent inhibitor, containing 16 amino acid residues with a Ki value of 2.45x10(-9) m for furin and of 5.60x10(-7) m for kexin, was designed with three incremental approaches. First, two nonessential Cys residues in the Lys fragment were deleted via a Cys-to-Ser mutation to minimize peptide misfolding. Second, residues in the reactive site of the inhibitor were replaced by the consensus substrate recognition sequence of furin, namely, Arg at P1, Lys at P2, Arg at P4 and Arg at P6. In addition, the P7 residue Asp was substituted with Ala to avoid possible electrostatic interference with furin inhibition. Finally, the extra N-terminal and C-terminal residues beyond the doubly conjugated disulfide loops were further truncated. However, all resultant synthetic peptides were found to be temporary inhibitors of furin and kexin during a prolonged incubation, with the scissile peptide bond between P1 and P1' being cleaved to different extents by the enzymes. To enhance proteolytic resistance, the P1' residue Ser was mutated to D-Ser or N-methyl-Ser. The N-methyl-Ser mutant gave rise to a Ki value of 4.70x10(-8) m for furin, and retained over 80% inhibitory activity even after a 3 h incubation with the enzyme. By contrast, the d-Ser mutant was resistant to cleavage, although its inhibitory activity against furin drastically decreased. Our findings identify a useful template for the design of potent, specific and stable peptide inhibitors of furin, shedding light on the molecular determinants that dictate the inhibition of furin and kexin.

Amino Acid Sequence↗

PubMed2006

Synthesis and biological activity of seleno sunflower trypsin inhibitor analog.

Sunflower trypsin inhibitor (SFTI-1) is a cyclic peptide with 14 amino acid residues and one disulfide bond. Its synthetic acyclic analog (aSFTI-1) with N-terminal Gly and C-terminal Asp was still active. Here, we report the synthesis of seleno aSFTI-1 with the disulfide bond of aSFTI-1 replaced by diselenide bond. The formation of the diselenide bond from selenol was achieved in a single step without the aid of oxidizing agent. For comparison, aSFTI-1 itself and aSFTI-1 with its disulfide bond replaced by two serines ([Ser(3,11)] aSFTI-1) were also synthesized. The trypsin inhibitory constants of seleno aSFTI-1, aSFTI-1 and [Ser(3,11)] aSFTI-1 were determined as 6.50 x 10(-9), 1.96 x 10(-9) and 8.10 x 10(-6) respectively, indicating that the disulfide bond is essential for the structure and function of aSFTI-1, and seleno aSFTI-1 is still active, although its inhibitory constant is reduced to 30% in comparison with that of aSFTI-1.

Amino Acid Sequence↗

PubMed2005

Macro-branched cell-penetrating peptide design for gene delivery.

Many kinds of macromolecular compounds that comprise a series of branches around an inner core have been made and showed some promises as DNA- and drug-delivery systems. In this study, a method for peptide polymer design having macro-branched peptide structure was adapted and it was applied for plasmid DNA delivery for the first time; acryloyl chloride was used by introducing the double bond into the N-terminal of HIV-1 tat (47-57, YGRKKRRQRRR). After being cleaved from resin, it was transformed to a polymer which possesses a poly-propionyl core matrix with tat branches and was named polytat by radical polymerization. After further separation and purification by Sephadex G150, polytat P1, polytat P2 and polytat P3 were acquired and the average molecular weight of the different macromolecules are 240, 178 and 82 kDa. We found that all these compounds complexed with plasmid DNA and showed significant transfection capabilities in a variety of mammalian cell lines, but acrylyl-tat or tat alone showed no significant transfection capability. Further study showed that polytat could be applied for plasmid DNA delivery for cell lines even with serum by endocytosis-mediated pathways.

Animals↗

PubMed2002

Electrochemical detection of parathion at a glassy-carbon electrode modified with hexadecane.

A modified electrode, based on a hexadecane (C(16))-coated glassy-carbon electrode (GCE) has been developed for the determination of parathion. The electrochemical behavior of parathion was investigated by cyclic voltammetry (CV). The peak potential and peak current were found to depend on the supporting electrolyte and the pH of the buffer solution. The reduction currents for parathion were proportional to parathion concentration over the range 8x10(-8)-2x10(-5) mol L(-1). The detection limit was 2x10(-8) mol L(-1) parathion for an accumulation time of 30 s. The effects of organic and inorganic species on the determination of parathion were also studied. A procedure was developed to extract parathion from spiked soil samples using a mixture of dichloromethane and acetone as the extraction solvent. The complete extraction and analytical procedure are simple, inexpensive and rapid. Parathion was determined in a soil sample by use of linear scan voltammetry (LSV).

Alkanes↗

PubMed2002

Isosteric replacement of A3 Val of porcine insulin by allo-Thr.

A3 Val is important for insulin activity. It is invariant in insulins from different species studied thus far. Based on the three dimensional structure of insulin, it was thought to be involved in receptor binding. Its replacement by Leu resulted in remarkable lowering of insulin activity, indicating the crucial requirement of the side chain geometry at this position. When A3 Val was replaced by Thr, which is hydrophilic but isosteric with Val, substantial insulin activity was retained. Therefore, the isosteric requirement for receptor binding at this site is more stringent than the hydrophobic requirement. Here we report the replacement of A3 Val of porcine insulin by the unnatural allo-Thr. The in vivo biological activity of A3 allo-Thr insulin is similar to that of A3 Thr insulin or native insulin, but its receptor binding activity is 7.6% instead of 50% for A3 Thr insulin, indicating that at the A3 position the hydrophilic OH group of Thr could be more tolerated in receptor binding than the OH group of allo-Thr. The retention of insulin activity by substituting A3 Val with the unnatural isosteric allo-Thr demonstrates again the importance of isosteric interaction in the binding of insulin with its receptor.

Animals↗