We describe a group of alloys that exhibit "super" properties, such as ultralow elastic modulus, ultrahigh strength, super elasticity, and super plasticity, at room temperature and that show Elinvar and Invar behavior. These "super" properties are attributable to a dislocation-free plastic deformation mechanism. In cold-worked alloys, this mechanism forms elastic strain fields of hierarchical structure that range in size from the nanometer scale to several tens of micrometers. The resultant elastic strain energy leads to a number of enhanced material properties.Mechanical properties, such as strength, of metallic materials are strongly affected by metallurgical processes such as heat treatment and plastic working, which bring modifications in the microstructure. On the other hand, these processes have no substantial effect on physical properties such as elastic modulus and thermal expansion. The reason for this is that the changes that can be affected by plastic working and heat treatment do not extend to interatomic bonds or electronic states.We present a group of alloys that exhibit multiple "super" properties and drastic changes in physical properties after plastic working at room temperature. These alloys simultaneously offer super elasticity, super strength, super coldworkability, and Invar and Elinvar properties. The alloys consist of Group IVa and Va elements and oxygen and share the following three electronic magic numbers: (i) a compositional average valence electron number [electron/atom (e/a) ratio] of about 4.24; (ii) a bond order (Bo value) of about 2.87 based on the DV-X␣ cluster method, which represents the bonding strength (1-3); and (iii) a "d" electron-orbital energy level (Md value) of about 2.45 eV, representing electronegativity. The properties emerge only when all three of these magic numbers are satisfied simultaneously. Various alloy composition combinations meet these criteria, such as Ti-12Ta-9Nb-3V-6Zr-O and Ti23Nb-0.7Ta-2Zr-O [mole percent (mol %)], wherein each alloy has a simple body-centered cubic (bcc) crystal structure. In order to exhibit these properties, each alloy system requires substantial cold working and the presence of a certain amount of oxygen, restricted to an oxygen concentration of 0.7 to 3.0 mol %.Typical properties of the alloys are shown in Fig. 1 for samples before and after cold swaging with 90% reduction in area (4). Tensile stress-strain curves shown in Fig. 1A indicate that cold working substantially decreases the elastic modulus and increases the yield strength and confirm nonlinearity in the elastic range, with the gradient of each curve decreasing continuously to about 1/3 its original value near the elastic limit. As a result of this decrease in elastic modulus and nonlinearity, elastic deformability after cold working reaches 2.5%, which is at least double the value before cold working. Generally, large elastic deformations that occur in so-called "super-elastic alloys" are known to be reversible martensitic transformations resulting from deformation, d...

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7 alpha-Hydroxysteroid dehydrogenase (7 alpha-HSDH;1 EC 1.1.1.159) is an NAD+-dependent oxidoreductase belonging to the short-chain dehydrogenase/reductase (SDR) 1 family. It catalyzes the dehydrogenation of a hydroxyl group at position 7 of the steroid skeleton of bile acids. The crystal structure of the binary (complexed with NAD+) complex of 7 alpha-HSDH has been solved at 2.3 A resolution by the multiple isomorphous replacement method. The structure of the ternary complex [the enzyme complexed with NADH, 7-oxoglycochenodeoxycholic acid (as a reaction product), and possibly partially glycochenodeoxycholic acid (as a substrate)] has been determined by a difference Fourier method at 1.8 A resolution. The enzyme 7 alpha-HSDH is an alpha/beta doubly wound protein having a Rossmann-fold domain for NAD (H) binding. Upon substrate binding, large conformation changes occur at the substrate binding loop (between the beta F strand and alpha G helix) and the C-terminal segment (residues 250-255). The variable amino acid sequences of the substrate-binding loop appear to be responsible for the wide variety of substrate specificities observed among the enzymes of the SDR family. The crystal structure of the ternary complex of 7 alpha-HSDH, which is the only structure available as the ternary complex among the enzymes of the SDR family, indicates that the highly conserved Tyr159 and Ser146 residues most probably directly interact with the hydroxyl group of the substrates although this observation cannot be definite due to an insufficiently characterized nature of the ternary complex. The strictly conserved Lys163 is hydrogen-bonded to both the 2'- and 3'-hydroxyl groups of the nicotinamide ribose of NAD(H). We propose a new catalytic mechanism possibly common to all the enzymes belonging to the SDR family in which a tyrosine residue (Tyr159) acts as a catalytic base and a serine residue (Ser146) plays a subsidiary role of stabilizing substrate binding.

The cofactor preferences exhibited by the enzymes of the SDR family are mainly determined by the electrostatic environment surrounding the 2'-hydroxyl (or phosphate) group of the adenosine ribose moiety of NADH (or NADPH). Thus, positively charged and negatively charged environments correlate with preference for NADPH and NADH respectively.

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Galectin-8 has much higher affinity for 3-O-sulfated or 3-Osialylated glycoconjugates and a Lewis X-containing glycan than for oligosaccharides terminating in Gal␤133/4GlcNAc, and this specificity is mainly attributed to the N-terminal carbohydrate recognition domain (N-domain, CRD) (Ideo, H., Seko, A., Ishizuka, I., and Yamashita, K. (2003) Glycobiology 13, 713-723). In this study, we elucidated the crystal structures of the human galectin-8-N-domain (-8N) in the absence or presence of 4 ligands. The apo molecule forms a dimer, which is different from the canonical 2-fold symmetric dimer observed for galectin-1 and -2. In a galectin-8N-lactose complex, the lactose-recognizing amino acids are highly conserved among the galectins. However, Arg 45 , Gln 47 , Arg 59 , and the long loop region between the S3 and S4 ␤-strands are unique to galectin-8N. These amino acids directly or indirectly interact with the sulfate or sialic acid moieties of 3-sialyl-and 3-sulfolactose complexed with galectin-8N. Furthermore, in the LNF-III-galectin-8N complex, van der Waals interactions occur between the ␣1-3-branched fucose and galactose and between galactose and Tyr 141 , and these interactions increase the affinity toward galectin-8N. Based on the findings of these x-ray crystallographic analyses, a mutagenesis study using surface plasmon resonance showed that Arg 45 , Gln 47 , and Arg 59 of galectin-8N are indispensable and coordinately contribute to the strong binding of galectins-8N to sialylated and sulfated oligosaccharides. Arg 59 is the most critical amino acid for binding in the S3-S4 loop region.Galectin-8 is a member of the galectin family, which share similar carbohydrate recognition domains (CRDs) 5 and affinity for ␤-galactosides (1, 2). Twelve galectins have been identified and characterized thus far. Each galectin has one (galectin-1, -2, -3, -5, -7, and -10) or two (galectin-4, -6, -8, -9, -11, and -12) conserved CRDs within a single molecule. According to the characteristics of their evolutionary conservation, wide tissue distribution, marked development-dependent expression, and abundance in specific tissues, galectins are presumed to function in various biological processes (3, 4). Galectin-8 is widely expressed and made up of two CRDs joined by a short linking peptide (1, 2). Recent studies have shown that galectin-8 modulates cell adhesion, spread, growth, and apoptosis (5-8). However, the precise recognition mechanisms and physiological roles of galectin-8 have not been fully elucidated.We determined the carbohydrate binding specificity of galectin-8 and found that it has much higher affinity for 3Ј-Osulfated or 3Ј-O-sialylated lactose and Lewis X-containing glycans than for oligosaccharides terminating in Gal␤133/ 4GlcNAc; this carbohydrate binding specificity was mainly attributed to the N-terminal CRD (N-domain) (9). The high affinity of galectin-8 for 3Ј-O-sialylated galactose is unique to this member of the galectin family (10); it is therefore of interest in determining its biological function via c...