Structural elements essential for

Many of the PS II inhibitors are herbicides liXe ureas, tria-zines, and aminotriazinones (reviewed in (5) and (6)). This class shares a common structural element essential for inhibitory potency, and their inhibitory potency depends on electronic, lipophilic and steric properties of the substituents. 

Okada H et al. (2008) Direct evidence revealing structural elements essential for the high binding ability of bisphenol A to human estrogen-related receptor-gamma. Environ. Health Perspect. 116(l) 32-38. 

Mossessova, E. and Lima, C. D. Ulpl-SUMO crystal structure and genetic analysis reveal conserved interactions and a regulatory element essential for cell growth in yeast. Mol. Cell 2000, 5, 865-76. 

Dual inhibitors have been reported, in which structural features essential for HDAC inhibition are combined with elements that are known to interact with other target classes. The recently reported multi-acting HDAC and EGFR/HER2 inhibitor 4 (Fig. 2) serves as an example to demonstrate this concept [52]. 

Aristotle recognised the importance of water by including it among the four elements along with fire, earth and air. In its many different functions, water is essential to the earth as we know it. Life critically depends on the presence of water. It is the medium of cells and is essential for the structure of proteins, cell membranes and DNA ". It has been estimated that more than 99 % of the molecules in the human body are actually water molecules". ... 

Self-assembling systems made of proteins provide many biological systems with essential structural elements, including viral envelopes, bacterial S-layers, microtubules, collagens, and keratins (see Ref. 6 for a review). Detailed studies on in vitro self-assembly optimization were carried out for several systems as a part of an ongoing effort to elucidate the in vivo mechanism. Data reported from such studies may provide an optional basis for the design and in vitro fabrication of nanostructures made of natural proteins (Fig. 1). 

It is a supposition that the )9-sheet structure of neurotoxin is an essential structural element for binding to the receptor. The presence of -sheet structure was found by Raman spectroscopic analysis of a sea snake neurotoxin (2). The amide I band and III band for Enhydrina schistosa toxin were at 1672 cm and 1242 cm" respectively. These wave numbers are characteristic for anti-parallel -sheet structure. The presence of -sheet structure found by Raman spectroscopic study was later confirmed by X-ray diffraction study on Laticauda semifasciata toxin b. 

In another study, ATPase reconstituted into liposomes was analyzed by infrared attenuated total reflection spectroscopy and the secondary-structure elements of the molecule were determined from the spectra obtained by Fourier self-deconvolution [42]. Gratifyingly, essentially identical secondary-structure estimates for the ATPase were obtained by this entirely different approach, suggesting quite strongly that these secondary-structure estimates are reasonably accurate. Thus, any future models for the structure of the H -ATPase must take this information into account. 

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