Volume 96, Issue 11, 01 December 2004
Index of content:
- APPLIED BIOPHYSICS (PACS 87)
96(2004); http://dx.doi.org/10.1063/1.1809269View Description Hide Description
Paramagnetic particle suspensions placed in a rotating unidirectional magnetic field form magnetic chains that rotate with the same frequency as the field. The motion of the fluid and particles surrounding the chain differs in phase and frequency from the chain rotation, a phenomenon that forms the basis of a sensitive detection scheme. Fluorescent particles that bind to the paramagnetic particles through their surface chemistry are used to demonstrate the concept. Epifluorescence video microscopy is used to capture images of the rotating chains. View windows placed over sequential images of rotating chains allows for measurement of the fluorescencebrightness in the window, which is composed of periodic signal from the steady rotation of the chain plus the background. A lock-in reference synchronized to the chain rotation is used to enhance the fluorescence signal from chain and improve signal to noise. Two different modes of chain rotation and signal collection are demonstrated. This technique can be used to develop a fast and sensitive, homogenous microdevice based solid-phase immunoassay.
96(2004); http://dx.doi.org/10.1063/1.1814412View Description Hide Description
We present a study of x-ray synchrotron radiation and neutronreflectivity on solid-supported lipid membranes prepared by spin coating. This technique has the advantage of allowing the control of the number of lipid layers by varying the deposition parameters. The experiments were performed on the cationic lipid 1,2-dioleoyl-3-trimethylammonium-propane chloride salt (DOTAP), the neutral lipid 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), the lipid mixture (DOTAP-DOPC), and the complex (DOTAP-DOPC∕DNA) deposited on wafers. Only single neutral lipids or lipid-peptide mixtures were deposited on solid substrate using the spin coating technique and characterized. Results on the structure of the deposited lipid layers indicate that DNA contributes to the order in the lipoplexes.