Evangelina E. Yguerabide

Resonance light scattering particles as ultrasensitive labels for detection of analytes in a wide range of applications

We have developed a new detection technology that uses resonance light scattering (RLS) particles as labels for analyte detection in a wide range of formats including immuno and DNA probe type of assays in solution, solid phase, cells, and tissues. When a suspension of nano sized gold or silver particles is illuminated with a fine beam of white light, the scattered light has a clear (not cloudy) color that depends on composition and particle size. This scattered light can be used as the signal for ultrasensitive analyte detection. The advantages of gold particles as detection labels are that (a) their light producing power is equivalent to more than 500,000 fluorescein molecules, (b) they can be detected at concentrations as low as 10−15 M in suspension by eye and a simple illuminator, (c) they do not photobleach, (d) individual particles can be seen in a simple student microscope with dark field illumination, (e) color of scattered light can be changed by changing particle size or composition for multicolor multiplexing, and (f) they can be conjugated with antibodies, DNA probes, ligands, and protein receptors for specific analyte detection. These advantages allow for ultra‐senstive analyte detection with easiness of use and simple and relatively inexpensive instrumentation. We have shown that our RLS technology can indeed be used for ultra‐sensitive detection in a wide range of applications including immuno and DNA probe assays in solution and solid phases, detection of cell surface components and in situ hybridization in cells and tissues. Most of the assay formats described in this article can be adapted for drug fast throughput screening. J. Cell. Biochem. Suppl. 37: 71–81, 2001.

Resonance light-scattering particles for ultra-sensitive detection of nucleic acids on microarrays

Resonance light-scattering particles for ultra-sensitive detection of nucleic acids on microarrays

Role of Membrane Fluidity in the Expression of Biological Functions

Biological membranes are composed of proteins, lipids, and carbohydrates. It is generally agreed that proteins are the components most directly responsible for the great diversity of functions displayed by natural membranes while the lipids, arranged in a bimolecular leaflet, provide a highly impermeable and supportive matrix for the proteins. Some of the membrane proteins, the so-called integral membrane proteins, extend into the hydrophobic regions of the lipid bilayer and are exposed on at least one of the membrane surfaces or may span the lipid bilayer and be exposed on both surfaces. Other membrane proteins, the peripheral proteins, are noncovalently attached to the membrane surface and do not extend significantly into hydrophobic regions of the membrane. The carbohydrates reside on the membrane surface, covalently attached to proteins or lipids. The lipid bilayer is not a static structure but can exist in different dynamic states in which the lipid molecules exhibit different degrees of rotational, segmental, and lateral mobilities. When mobility is high, the membrane is said to be in a high fluid state and free membrane proteins can readily translate and rotate in the lipid bilayer.

Fluorescence spectroscopy in biological and medical research

Abstract Fluorescence spectroscopy is one of the most sensitive and versatile tools in medical, biological and biochemical research. Here we discuss the use of (1) polarized fluorescence spectroscopy to study the conformational dynamics of proteins, (2) fluorescence recovery after photobleaching to study lateral mobility of proteins and lipids in biological cell membranes and (3) excitation energy transfer to measure distances between interesting sites in macromolecules and biological membranes.