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Mingdi Yan

Publications and source records attributed to Mingdi Yan.

5 recordsLinked to original sources
PubMed2006

Surface and interface control on photochemically initiated immobilization.

Surface and interface properties are important in controlling the yield and efficiency of the photochemically initiated immobilization. Using a silane-functionalized perfluorophenyl azide (PFPA-silane) as the photoactive cross-linker, the immobilization of polymers was studied by adjusting the density of the surface azido groups. Dilution of the photolinker resulted in a gradual decrease in the density of surface azido groups as well as the thickness of the immobilized film. When a nonphotoactive silane was added to PFPA-silane, the film thickness decreased more rapidly, suggesting that the additive competed with PFPA-silane and effectively reduced the density of the surface azido groups. The effect of surface topography was studied by adding a nonphotoactive silane with either a shorter (n-propyltrimethoxysilane (PTMS)) or a longer spacer (n-octadecyltrimethoxysilane (ODTMS)). In most cases the long chain ODTMS shielded the surface azido groups, resulting in a more rapid decrease in film thickness as compared to PTMS treated under the same conditions. As the density of the surface azido groups decreased, the immobilized polymer changed from smooth films to patched structures and, eventually, single polymer molecules.

Microscopy, Atomic Force↗
PubMed2004

Theoretical model for photochemical or thermally activated immobilization of macromolecules.

The covalent immobilization of macromolecules on surfaces and within 3-dimensional networks is quantitatively described using a model based on Poisson statistics. This model determines the immobilized density or layer thickness as a function of molecular weight of the macromolecule or radiant exposure prior to and following the surface deposition of the macromolecule. Measurements of immobilized layer thickness provide first-order rate constants for decomposition of the surface-bound linker molecules and an estimate of the surface-bound linker density. The model predicts the relative density of immunocomplexed antibodies as a function of the irradiation time used to immobilize antigens. By providing the average number of bonds to the immobilized molecule, the model enables studies of the effect of multiple bonds on the activity of biomolecules. Experimental data by the authors and from the literature validate the model.

Journal Article↗
PubMedDate not supplied

Fluorescence anisotropy studies of molecularly imprinted polymers.

A molecularly imprinted polymer (MIP) is a biomimetic material that can be used as a biochemical sensing element. We studied the steady-state and time-resolved fluorescence and fluorescence anisotropy of anthracene-imprinted polyurethane. We compared MIPs with imprinted analytes present, MIPs with the imprinted analytes extracted, MIPs with rebound analytes, non-imprinted control polymers (non-MIPs) and non-MIPs bound with analytes to understand MIP's binding behaviour. MIPs and non-MIPs had similar steady-state fluorescence anisotropy in the range 0.11-0.24. Anthracene rebound in MIPs and non-MIPs had a fluorescence lifetime of tau = 0.64 ns and a rotational correlation time of phi(F) = 1.2-1.5 ns, both of which were shorter than that of MIPs with imprinted analytes present (tau = 2.03 ns and phi(F) = 2.7 ns). The steady-state anisotropy of polymer solutions increased exponentially with polymerization time and might be used to characterize the polymerization extent in situ.

Fluorescence Polarization↗