Pressure-actuated microfluidic devices for electrophoretic separation of pre-term birth biomarkers.

We have developed microfluidic devices with pressure-driven injection for electrophoretic analysis of amino acids, peptides, and proteins. The novelty of our approach lies in the use of an externally actuated on-chip peristaltic pump and closely spaced pneumatic valves that allow well-defined, small-volume sample plugs to be injected and separated by microchip electrophoresis. We fabricated three-layer poly(dimethylsiloxane) (PDMS) microfluidic devices. The fluidic layer had injection and separation channels, and the control layer had an externally actuated on-chip peristaltic pump and four pneumatic valves around the T-intersection to carry out sample injection. An unpatterned PDMS membrane layer was sandwiched between the fluidic and control layers as the actuated component in pumps and valves. Devices with the same peristaltic pump design but different valve spacings (100, 200, 300, and 400 µm) from the injection intersection were fabricated using soft lithographic techniques. Devices were characterized through fluorescent imaging of captured plugs of a fluorescein-labeled amino acid mixture and through microchip electrophoresis separations. A suitable combination of peak height, separation efficiency, and analysis time was obtained with a peristaltic pump actuation rate of 50 ms, an injection time of 30 s, and a 200-µm valve spacing. We demonstrated the injection of samples in different solutions and were able to achieve a 2.4-fold improvement in peak height and a 2.8-fold increase in separation efficiency though sample stacking. A comparison of pressure-driven injection and electrokinetic injection with the same injection time and separation voltage showed a 3.9-fold increase in peak height in pressure-based injection with comparable separation efficiency. Finally, the microchip systems were used to separate biomarkers implicated in pre-term birth. Although these devices have initially been demonstrated as a stand-alone microfluidic separation tool, they have strong potential to be integrated within more complex systems.

Conformationally controlled mechanistic aspects of BACE 1 inhibitors.

This study highlights conformationally controlled mechanistic aspects of peptide inhibitors for BACE 1. Peptide inhibitors with reduced molecular weight tend to have cyclic conformation leading to reduced interactions with catalytic motif. Conformation plays a major role in determining potency of peptide inhibitors. An attempt has been made at designing lead compound with reduced molecular weight along with proper conformation suitable for active site and retention of specificity analogous to natural substrate. Reduced molecular weight should hopefully lead to enhanced bioavailability.

Perspectives in designing anti aggregation agents as Alzheimer disease drugs.

Ab initio molecular orbital calculations at the Hartree-Fock level have been performed for middle portion of amyloid beta that can be best utilized to design intercalative type of preventive drug molecules. Metal induced self assemblage tendency of 16-23 residues' piece of Abeta and its affinity for different metal ions have been investigated in detail. Based on energetics of self aggregation and charge complementarity aspects, two intercalative type of lead compounds have been designed; their preventive mode of actions have been predicted and compared to other drugs of this category. Designed compounds may also exercise their preventive action by removing metal toxicity. Exact mode of action would perhaps depend on relative concentrations of metal ion and amyloid beta.