Two-dimensional crystallization of streptavidin by nonspecific binding to a surface film: study with a scanning electron microscope

Abstract

A two-dimensional (2D) crystal of streptavidin has been obtained by a nonspecific binding method. The protein molecules were bound and formed a dense packing on the film of poly(1-benzyl-L-histidine) spread at the surface of protein solution. The surface film was moderately heated to stimulate crystallization of bound streptavidin. A potential of this method for obtaining 2D crystals of soluble proteins is demonstrated. The present 2D crystal structure of streptavidin resembles that previously obtained by specific binding to biotinylated lipid. We show in addition that the 2D array of protein with usual size-50 A can be imaged using a high resolution scanning electron microscope (HR-SEM) and subject to structural analysis at low resolution. Various limitations in HR-SEM degrade considerably the image quality. However, the usability of a bulk plate as specimen support would make HR-SEM a convenient tool, when such a substrate must be considered in application of protein arrays, and if an intrinsic low resolution is acceptable.

Helical Crystallization of Proteins on Carbon Nanotubes: A First Step towards the Development of New Biosensors

“…These ligands have enabled one-pot syntheses of some spectacular high-nuclearity aggregates, often with interesting magnetic and electronic properties. [9] Thus, each planar [M(L)] moiety has available two acceptor sites on M II to form a 1808 junction, and two carboxylates donors forming 908 junctions to one another and to the acceptor sites on M II . Recent developments in self-assembly have shown how metal ± ligand frameworks can be sucessfully templated about a substrate anion [6] or cation.…”

“…Streptavidin has become very useful in many biochemical assays, such as labeling and affinity chromatography because of its high affinity for ()biotin (K a % 10 15 ). This observation was not surprising since streptavidin can be purified on hydrophobic resins such as benzyl-DC beads of cellulose, [8] can form 2D crystals on nonspecific hydrophobic lipid films, [9] and binds strongly to plain carbon-coated electron microscopy grids. In appropriate conditions the tubes were almost completely covered by streptavidin whereas only a few free molecules could be seen in the background of the electron microscope grid.…”

Two-dimensional protein crystallization via metal-ion coordination by naturally occurring surface histidines.

“…A number of proteins have been crystallized at interfaces by targeting to surface-bound affinity ligands (1,5), by electrostatic interactions (6), and by metal coordination by polyhistidine-tagged proteins (7). The first approach requires synthesis of a lipid displaying an appropriate affinity ligand (8)(9)(10).…”

“…The three-dimensional structure of streptavidin has been well characterized (16)(17)(18)(19), and the protein is known to crystallize two dimensionally beneath monolayers of biotinylated lipids (20). 2D crystallization of streptavidin has also been induced by electrostatic interactions with a monolayer of poly(1-benzyl-L-histidine) (6). Streptavidin contains two surface-accessible histidine residues per subunit at positions 87 and 127 (18,19), which, combined with the available structural information, make streptavidin an attractive model system for investigating this 2D crystallization approach.…”

Monomolecular Layer Formation of Amphiphilic Chromoionophore I at the Air/Water Interface

“…[1][2][3] Although little is known about the formation mechanism of 2D array assembly of soluble functional proteins at interfaces such as air/water, air/graphite, air/metal, water/graphite, water/organic liquid, water/metal liquid, and air/liquid/water, a growing number of examples are studied from which we may be able to learn physical and chemical principles governing these processes. [4][5][6][7][8] The development of sensors with an optical transduction of the chemical recognition process has become a highly relevant and rapidly expanding enterprise in analytical chemistry, nanotechnology, and nanobioengineering. 9 Neutral ionophores have been used as a form of ion selective electrodes in a solvent polymeric membrane matrix, which allows the potentiometric determination of many physiologically relevant ions.…”