Abstract: The method provides for attaching nucleic acids to a surface at a controlled grafting density in a controlled conformation by contacting an immobilization solution of nucleic acids containing at least one block of adenine nucleotides to a surface for a sufficient period of time to allow attachment to the surface. Another aspect of the methods described provides for controlling the grafting density of immobilized oligonucleotides by coadsorption/displacement by oligo(dA). Another aspect provides for a method of immobilizing oligonucleotides in complex conformations by varying the number and position of the block(s) of adenine nucleotides in the sequence of said oligonucleotides. Another aspect provides for controlled immobilization of a functional unit, such as a ligand, a molecule, a macromolecule, an aptamer, a lectin, an immunoglobulin, an antibody, a biomolecule, a solid state particle, a vesicle, or a label to a surface via attachment to at least one block of adenine nucleotides.

Abstract: A method is provided for observing mixing interactions and reactions of two materials in a fluid. The method in one form provides for concentrating by balancing electrophoretic velocities of a material against the bulk flow of fluid in the presence of a temperature gradient. Using an appropriate fluid, the temperature gradient can generate a corresponding gradient in the electrophoretic velocity of the material so that the electrophoretic and bulk velocities sum to zero at a unique position and the material will be focused at that position. A second material can then be introduced into the fluid and allowed to move through and interact with the focused band of the first material. Products of the interaction can then be detected as they are focused at a different position along the gradient. The method can be adapted to study the temperature dependence of the molecular interaction.