Protein structure, images

Ai HW, Henderson JN, Remington SJ, Campbell RE (2006) Directed evolution of a monomeric, bright and photostable version of Clavularia cyan fluorescent protein structural characterization and applications in fluorescence imaging. Biochem J 400 531-540... 

We are currently pursuing protein crystallization imaging in microfluidic devices, which can use both THG and CARS microscopy. The use of the microfluidic platform is the newest and one of the most promising trends in the colossal project of obtaining the exact structure of more than 70,000 protein molecules. The goal is to use microfluidic devices as a multifunctional, multiparallel platform for trying out a... 

Figure 6.18 Transmission electron micrographs of protein structures from solutions of 3 wt% a-lactalbumin incubated with 4 wt% Bacillus licheni-forrnis at 50 °C (75 mM Tris-HCl, pH = 7.5) at different values of the cal-cium/a-lactalbumin molar ratio R. The image dimensions are 2100 nrn x 2600 nm Reproduced from Gravcland-Bikkcr et al. (2004) with permission.

Cohen, C., and Vibert, P. J. (1987). Actin filaments Images and models. In Fibrous Protein Structure (J. M. Squire and P. J. Vibert, Eds.). Academic Press, New York. 

Protein structure The three-dimensional structure of a protein can be determined almost to the determination atomic level by the techniques of X-ray crystallography and nuclear magnetic resonance (NMR) spectroscopy. In X-ray crystallography a crystal of the protein to be visualized is exposed to a beam of X-rays and the resulting diffraction pattern caused as the X-rays encounter the protein crystal is recorded on photographic film. The intensities of the diffraction maxima (the darkness of the spots on the film) are then used to mathematically construct the three-dimensional image of the protein crystal. NMR spectroscopy can be used to determine the three-dimensional structures of small (up to approximately 30 kDa) proteins in aqueous solution. 

It has been found out that the structure of proteins is flexible and there are many differences between the static spatial image of a protein and a dynamic view of its structure. This divergence is caused by the fact that the repetitive part of a-helices and [3-strands of protein folds, often described as a succession of secondary structures, can assume different local spatial orientation. Two experimental methods can be used to measure the flexibility in precise regions of protein structures (the anatomic mean square displacement, B-factor, measured during crystallographic experiments, and indirectly by NMR experiments which show different local conformation that could correspond directly to different stages of protein structures) (Bornot et al., 2007). 

Figure 8.2 Electron microscopic image of a collagen microfibril. Superimposed on this are arrows representing tropocollagen molecules in the N to C direction. The gap between the N-terminus of one molecule and the C-terminus of another is 400 A. The bands correspond to the gaps. (Reproduced by permission from Walton AG. Polypeptide and Protein Structure. New York Elsevier, 1981, p. 116.)...

Images of three-dimensional protein structures are often rendered using cartoon-like ribbons to indicate common features of the carbon backbone, such as a-helices and /-i-sheets. Casually browsing the structures illustrated in a biology textbook or an online database, one is struck by the frequent appearance of the right-handed helical structures known as a-helices. The structural features of a-helices are illustrated in Figures 10.1 and 10.2. 

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