Why is sialic acid attracting interest now? Complete enzymatic synthesis of sialic acid with N-acylglucosamine 2-epimerase

N-Acetylneuraminic acid (NeuAc), the representative of the family of sialic acids, is an important molecule in biological recognition systems. Currently, NeuAc-based novel pharmaceutical agents and diagnostic reagents for influenza viruses are highly required in medical fields, and larger amounts of NeuAc are in demand worldwide. NeuAc had been prepared either from colominic acid (a homopolymer of NeuAc) produced by fermentation or from natural sources such as edible bird's nests, milk or eggs. However, the drawbacks of such conventional methods make them unsuitable for large-scale production of NeuAc. Recently, the N-acylglucosamine 2-epimerase (AGE) gene from porcine kidney was cloned in E. coli, and a strain with a high AGE expression level was constructed for practical applications, which enabled the complete enzymatic synthesis of NeuAc with a high conversion rate from the substrates, namely, N-acetylglucosamine and pyruvate. In addition, NeuAc of highest purity could be produced economically via its direct crystallization from the reaction mixture without any column purification processes. Such a simple procedure promises to be applicable to the mass production of sialic acid at the lowest cost.     

Thermodynamic studies on the helix-sense inversion of polyaspartates in the solid state

The Clapeyron analysis has been performed on polyaspartate samples (–[NH–CH(CH₂C(O)OX)C(O)]_n–) carrying side chains such as X = benzyl (1PLA), phenethyl (2PLA), phenylpropyl (3PLA), and phenoxyethyl (PPOLA). In all cases examined, the unwinding and rewinding process of the helical backbone is consistent with the zippering mechanism previously elucidated for the concentrated LC solution. Variation of the PVT properties such as the volume and enthalpy changes at the transition was carefully examined. In the bulk solid state, contribution from the thermodynamic quantities associated with the redistribution of molecules in the configurational space (molecular packing) becomes substantial. It has been concluded that the characteristic features of the ?-α|?-ω transition of 1PLA (140 °C) are inconsistent with the Clapeyron concept, suggesting that the phase transition may involve a non-equilibrium step. The r-α|?-ω transitions of the other polymers were found to conform to the Clapeyron relation. The screw-sense inversion seems to be reversible only when the crystalline structure (hexagonal) remains unaltered before and after the transition. The purpose of this work is to elucidate the key factor responsible for the reversibility of the solid-sate transition, thus providing a basis to understand the role of flanking side chains.     

Empowering nature conservation in Japanese rural areas: a planning strategy integrating visual and biological landscape perspectives

There has been much discussion about the importance of nature conservation, but a concrete strategy has been lacking. Most conservation measures are reactive to development projects that threaten the sites’ conservation values. There is little synergy between nature conservation and other competing land-use policies. Furthermore, conservation messages are not communicated well because there are few opportunities for those involved in research, policy formation and policy implementation to interact. We illustrate the methodological framework that can be used to address these issues in rural nature conservation by presenting our research conducted in the Arai-Keinan district of Niigata, Japan. The proposed methodological framework consists of integrating visual and biological landscape approaches to understand the area’s natural environment and using participatory research to narrow the communication gaps among those involved. We stress the importance of expressing the research results and recommendations on a map as a strategy for effective nature conservation. The graphical presentation of a map not only allows for clearer delivery of messages from researchers to government officials and residents, but also facilitates coordination among competing land-use policies. The map is the central ammunition in reversing the reactive nature of conservation policies to that of a “preemptive” nature. Future research directions to gain stronger political support are also discussed.     

Cholesteryl moiety terminated amphiphilic polymethacrylates containing nucleic acid bases for drug delivery

Poly[9‐(2‐methacryloyloxyethyl)adenine] and poly[1‐(2‐methacryloyloxyethyl)thymine] with one pendant cholesteryl moiety at the polymer end (PMEA‐Chol, PMET‐Chol) and with two pendant cholesteryl moieties at both polymer ends as terminal groups (PMEA‐2Chol, PMET‐2Chol) were prepared by radical polymerization of 9‐(2‐methacryloyl‐oxyethyl)adenine (MEA) and 1‐(2‐methacryloyloxyethyl)thymine (MET) initiated with 4,4′‐azobis[(3‐cholesteryl)‐ 4‐cyanopentanoate] in the presence of 2‐mercaptoethanol or thiocholesterol as chain transfer reagents, respectively. The copolymers [PNiPAAm‐co‐PMEA‐nChol (n = 1,2)] composed of N‐isopropylacrylamide (NiPAAm) and MEA were also prepared in a similar manner. The self‐organization of these polymers and copolymers was confirmed by a fluorescence measurement, and then their critical concentrations of micelle formation (CMC) were determined. The mixture of PMEA‐2Chol and cholesterol as a lipophilic drug model formed a lamella type of complex with an interplaner spacing of d = 35.3 Å. The hypochromism based on the formation of a 1 : 1 interaction of adenine and thymine moieties was found to appear in the mixed aqueous solution of PMEA‐Chol and PMET‐Chol. Complementary interactions were also confirmed in the system of PMET‐2Chol and adenosine as well as PMEA‐2Chol and uridine. Cis‐dichlorodiammine platinum(II) (CDDP) was bound to PNiPAAm‐co‐PMEA‐Chol through the adenine moiety by ligand substitution atoms of CDDP. The amount of CDDP loaded on the copolymer was found to be 0.143 g g^?1. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 3064–3075, 2007     

Morphological abstraction of thyroid tumor cell nuclei using morphometry with factor analysis

Various morphonuclear studies by digital image analysis have successfully been applied to quantify the nuclear morphology, including chromatin distribution pattern, in cytology of various organs; however, the majority of past reports have not shown correlation between the quantitative data by digital image analysis and cytological findings in practical diagnosis. In this report, we present the usefulness of morphological abstraction to combine the objective data and subjective observation in cytological diagnosis. Randomly selected, 100 cells in each Papanicolaou-stained ABC smear samples of 39 benign and malignant thyroid tumor cases were studied. Gray-level image data provided seven parameters for nuclear size, four parameters for nuclear shape, and 16 parameters showing the nuclear chromatin patterns from high-dimensional texture analysis of using co-occurrence and run-length matrices. To statistically abstract nuclear morphology, factor analysis was used. Factor analysis classified morphological nuclear characters as abstraction parameter into five abstract parameters composed of nuclear size, shape, heterogeneity, and contrast and homogeneity of chromatin pattern. The nuclei of papillary carcinoma showed larger size, more irregular shape, and higher contrast of chromatin pattern than those of the benign group. The follicular carcinomas have larger nucleus in each cell and more monotonous chromatin pattern among cells in each case than those of the benign group. Morphological abstraction by morphometry with factor analysis may provide a practical approach to the detection of the underlying characteristics of nuclear morphology in aspiration biopsy cytology.     

Automatic system test technology of virtual machine software patch on IaaS cloud

Regarding IaaS virtual machine operations, the problem is its high operation costs because users need to distribute and verify software patches for their virtual machines. We proposed an automatic verification technology for each virtual machine patch in our previous work. In this paper, we study an improvement of automatic verifications of system tests with plural virtual machines. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

High-cycle fatigue crack initiation and growth in TIMETAL LCB

This investigation has examined the influence of grain boundary α contiguity on the high-cycle fatigue behavior of aged TIMETAL LCB, with the fatigue performance being evaluated under tension-tension loading conditions atR=0.1 in laboratory air and 25 Hz. Fractographic analysis indicated that fatigue initiation, independent of processing history, involved subsurface crack formation. Serial section studies also indicated that crack initiation occurred at the interface between the triple-point α and the aged β matrix. Further back-scattered electron microscopy examination of the aged microstructures indicates that the observed differences in high-cycle fatigue behavior can be understood by considering the effect of processing history on the connectivity of grain boundary α, with decreased connectivity being associated with enhanced fatigue performance. This paper was presented at the Beta Titanium Alloys of the 00’s Symposium sponsored by the Titanium Committee of TMS, held during the 2005 TMS Annual Meeting & Exhibition, February 13–16, 2005 in San Francisco, CA.     

Chemical trends of the band gaps of idealized crystal of semiconducting silicon clathrates, M8Si38A8 (M = Na, K, Rb, Cs; A = Ga, Al, In), predicted by first-principle pseudopotential calculations

We have calculated the band structures of Si clathrate, M₈Si₃₈Ga₈ (M = Na, K, Rb, and Cs), using the density-functional theory under the generalized gradient corrected local density approximation, where M is the encapsulated guest alkali atom. They are found to be indirect semiconductors with the calculated gaps (E_g) from 0.45 to 0.89 eV, which should be compared to the calculated gap of 0.65 eV of crystalline Si with the diamond structure. The gaps become wider with the promotion to the heavier guest alkali atoms and the reasons of gap widening are discussed using the calculated dependence of E_g on the cell-volume of guest-free silicon clathrate (Si₄₆). Effect of the substitutional elements in the clathrate framework (Al and In in place of Ga) was also discussed.     

Beetle elytron plate and the synergistic mechanism of a trabecular-honeycomb core structure

For the development of lightweight biomimetic materials, the compressive properties of the beetle elytron plate(BEP, a type of biomimetic sandwich plate inspired from beetle elytra) and the underlying mechanism thereof were investigated. With the following results:(1) The shared mechanism of trabeculae was revealed by using structural analysis. It is further predicted that a BEP with hollow trabeculae should possess enhanced compressive properties.(2) When the trabecular number(N) in a hexagonal unit of the honeycomb is less than three, the compressive strength of the BEP is rapidly increased with the increment of N. When N is over four, the deformation capacity is significantly improved because of the arising of S-type buckling deformation in the core structure of the BEP. Furthermore, the definition of the BEP is proposed combined with the biological structure of the beetle elytra.(3) When N=6 and the external diameter of trabeculae is equal to the length of honeycomb walls, the synergistic mechanism between the trabeculae and the honeycomb walls in BEPs is fully exerted. Namely, the trabecula restricts the deformation of the honeycomb walls; in turn, the honeycomb walls provide lateral support for the trabecula. This mechanism leads the core in the BEP to generate an S-type global buckling deformation producing the best compressive properties. The results will greatly impact the biomimetic field of beetle elytra and many industries in which honeycomb structure also serves as a key component.     

Synthesis of carbon nanotubes on Ni/carbon-fiber catalysts under mild conditions

Methane, n-hexane, benzene, and cyclopentadiene were decomposed at a relatively mild temperature (773 K) over a Ni catalyst supported on either vapor grown carbon fibers (VGCF) or graphitized carbon fibers (GCF). Transmission electron microscopy showed that the morphology of the fibers changed according to hydrocarbon and particle size. Decomposition of methane and n-hexane produced fishbone-type fibers. The fibers from n-hexane sometimes showed intermittent hollow structures but the diameters of the fibers were widely distributed. Decomposition of benzene and cyclopentadiene mainly produced winding type carbon nanotubes of relatively uniform diameters (10-20 nm). Bidirectional fishbone-type fibers (fibers growing outward from a central catalyst particle) were also observed as a by-product. Small Ni particles (10-20 nm) with stretched tails were present on the tips of tubular fibers, some of which frequently changed growth direction. The varying tubular morphologies can be ascribed to liquid-like Ni particles resulting from the freezing point depression due to a fast dissolution of carbons during decomposition of benzene or cyclopentadiene. The formation of bidirectional fibers was also observed in the decomposition of n-hexane. Relatively large well-faceted Ni particles (diameter 50-110 nm) grew bidirectional fibers.