Preservation of the biofunctionality of DNA and protein during microfabrication

Microfabrication processes, especially in silicon, are not compatible with biomolecules. Silicon and metal-based materials having crystalline structures are manipulated under harsh conditions with acids, bases, and organic solvents at high temperature. In comparison, organic biomolecules such as DNA and proteins have complex, three-dimensional structures and are sensitive to denaturation, oxidation, hydrolysis, and thermal destruction. Here, we report on the integration of DNA and the biotin-binding protein NeutrAvidin into microfabrication processes by using a novel approach based on a gold passivation mask. Our data show that this passivation method preserves approximately 84% of the biofunctionality of DNA and approximately 30% of that of NeutrAvidin under harsh process conditions. This novel technology enables the integration of DNA, proteins, and potentially other biological molecules into mass scalable microfabrication processes for biomedical devices, biochips, biosensors, and microelectromechanical systems with biomolecules (BioMEMS).     

A simple and efficient colorimetric anion sensor based on a thiourea group in DMSO and DMSO-water and its real-life application

An efficient colorimetric sensor with a thiourea moiety as binding sites and p-nitrophenylhydrazine as a signaling unit has been synthesized by only one single-step procedure. Selectivity for anions with the distinct geometry (tetrahedral, trigonal planar and spherical) has been investigated in dry DMSO and even in DMSO/H(2)O (95:5, v/v) solutions through the naked-eye experiment, UV-vis titration and (1)H NMR titration techniques. In particular, the fluoride of toothpaste can be detected qualitatively by the sensor 1.     

Manipulating DNA writhe through varying DNA sequences

It is demonstrated that the shapes and magnitudes of DNA writhe can be precisely manipulated solely through maneuvering the nucleotide sequence of DNA and without the assistance of topoisomerases.     

Synthesis and photophysical studies of calix[4]arene-based binuclear platinum(II) complexes: probing metal-metal and ligand-ligand interactions

A series of calix[4]arene-based binuclear platinum(II) complexes, Pt2LCl2 (1, L = 5,11,17,23-tetra- tert-butyl-25,27-di[methoxy(4-phenyl)-(C;N;N)]-26,28-dihydroxycalix[4]arene, HC;N;N = 6-phenyl-2,2'-bipyridine), [Pt2L(mu-dppCn)](ClO4)2 (dppCn = bis(diphenylphosphino)-methane (2, n = 1), -ethane (3, n = 2), -propane (4, n = 3), and [Pt2L(PPh3)2](ClO4)2 (5), have been designed and synthesized in this work. Spectroscopic investigation demonstrates that p- tert-calix[4]arene is capable of assembling the two square-planar [(C;N;N)Pt(II)] units in a face-to-face manner, simultaneously suppressing intermolecular aggregation and increasing the solubility of the studied complexes. Facile replacement of the chloride ligand in 1 by the strongly sigma-donating ancillary phosphine ligands affords binuclear platinum(II) complexes with improved photophysical properties. All of the complexes are emissive both in the fluid/glassy solution and in the solid state, except for 1 in the solid state at room temperature. Moreover, the absorption and emission energies of the complexes are sensitive to the ancillary ligands. Varying the tethered phosphine auxiliaries from dppm (2) and dppe (3) to dppp (4) and PPh3 (5) modulates the intramolecular metal-metal (Pt...Pt) and ligand-ligand (pi-pi) distances, thereby leading to a switch of 3MMLCT and excimeric 3(pipi*) excited states to a common 3MLCT excited state.     

Carbon nanodots as peroxidase mimetics and their applications to glucose detection

Carbon nanodots (C-Dots) were found to possess intrinsic peroxidase-like activity, and could catalytically oxidize 3,3',5,5'-tetramethylbenzidine (TMB) by H(2)O(2) to produce a colour reaction. This offers a simple, sensitive and selective colorimetric method for glucose determination in serum.     

Binaphthol-derived bisphosphoric acids serve as efficient organocatalysts for highly enantioselective 1,3-dipolar cycloaddition of azomethine ylides to electron-deficient olefins

A variety of chiral bisphosphoric acids derived from binaphthols have been evaluated for enantioselective 1,3-dipolar cycloaddition reactions, revealing that the feature of the linker in the catalysts exerted great impact on the stereoselectivity. Among them, the oxygen-linked bisphosphoric acid 1a provided the highest level of stereoselectivity for the 1,3-dipolar cycloaddition reaction tolerating a wide range of substrates including azomethine ylides, generated in situ from a broad scope of aldehydes and α-amino esters, and various electron-deficient dipolarophiles such as maleates, fumarates, vinyl ketones, and esters. This reaction actually represents one of the most enantioselective catalytic approaches to access structurally diverse pyrrolidines with excellent optical purity. Theoretical calculations with DFT method on the formation of azomethine ylides and on the transition states of the 1,3-dipolar cycloaddition step showed that the dipole and dipolarophile were simultaneously activated by the bifunctional chiral bisphosphoric acids through the formation of hydrogen bonds. The effect of the bisphosphoric acids on reactivity and stereochemistry of the three-component 1,3-dipolar cycloaddition reaction was also theoretically rationalized. The bisphosphoric acid catalyst 1a may take on a half-moon shape with the two phosphoric acid groups forming two intramolecular hydrogen bonds. In the case of maleates, one phosphate acts as a base to activate the 1,3-dipole, and simultaneously, the two hydroxyl groups in the catalyst 1a may respectively form two hydrogen bonds with the two ester groups of maleate to make it more electronically deficient as a much stronger dipolarophile to participate in a concerted 1,3-dipolar cycloaddition with azomethine ylide. However, in the cases involving acrylate and fumarate dipolarophiles, only one hydroxyl group forms a hydrogen bond with the ester functional group to lower the LUMO of the C-C double bond and another one is remained to adjust the acidity and basicity of two phosphoric acids to activate the dipole and dipolarophile more effectively.     

One-pot synthesis of Cu1.94S-CdS and Cu1.94S-Zn(x)Cd(1-x)S nanodisk heterostructures

Nanodisk heterostructures consisting of monoclinic Cu(1.94)S and wurtzite CdS have been colloidally synthesized for the first time. Initially, hexagonal-shaped nanodisks of Cu(1.94)S were produced upon thermolysis of a copper complex in a solvent mixture of HDA and TOA at 250 °C. Rapid addition of Cd precursor to the reaction mixture resulted in the partial conversion of Cu(1.94)S into CdS, yielding Cu(1.94)S-CdS nanoheterostructures. The original morphology of the Cu(1.94)S nanodisks was conserved during the transformation. When Zn precursor was added together with the Cd precursor, Cu(1.94)S-Zn(x)Cd(1-x)S nanodisks were generated. These two-component nanostructures are potentially useful in the fabrication of heterojunction solar cells.