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Biomedical subjects

S Shinkai

Publications and source records attributed to S Shinkai.

At least 19 recordsLinked to original sources
PubMed2006

Risk factors for dietary variety decline among Japanese elderly in a rural community: a 8-year follow-up study from TMIG-LISA.

OBJECTIVE: To examine the factors related to the decline of dietary variety among the rural community-dwelling Japanese elderly people and the implication on the planning of elderly people's nutritional improvement program in the future. DESIGN: A prospective cohort study during 8-year follow-up from 1992 to 2000. SETTING: This study was conducted in Nangai Village, a rural and mainly agricultural area of Akita Prefecture in the northern part of Honshu, one of four main islands in Japan. SUBJECTS: A total of 417 elderly people (160 men, 257 women) who completed interviews and food intake frequency surveys conducted in 1992, 1994, 1996, 1998, and 2000 were studied. METHODS: Dietary variety and variables potentially associated with dietary variety decline were identified from a face-to-face interview at the baseline and 8-year follow-up surveys. The dietary variety was measured using the dietary variety score (DVS), which covers the 10 main food groups in Japanese meals. RESULTS: During the 8-year follow-up, 36.2% of the subjects showed a decline in dietary variety. Health characteristics also change among the 8-year follow-up and these changes have an effect on the decline of dietary variety. Significant predictors for decline in dietary variety included loss of spouse, deterioration in self-perceived chewing ability, and decrease in intellectual activity score. CONCLUSIONS: Loss of spouse, deterioration in chewing ability, and decline in intellectual activity may increase the risk of decline in dietary variety in community-dwelling Japanese elderly people.

Activities of Daily Living↗
PubMed2004

A study of boronic acid based fluorescent glucose sensors.

Boronic acid based anthracene dyes were designed, synthesized, and immobilized to solid phase, creating a continuous glucose sensor. Glucose sensitivities of dyes can decrease drastically after immobilization, therefore how to immobilize a dye to solid phase without changing the dye property is a key issue in developing the sensor. The glucose sensitivity of the simplest 1st generation sensor, which is based on an immobilized mono-phenylboronate/single-arm type, came short of the sensitivity requirement for practical use, because of the very moderate fluorescence intensity change over the physiological glucose range. However, the 2nd generation, an immobilized bis-phenylboronate/double-arm type sensor, which contained two boronate groups in the dye moiety in expectation of a large intensity change, brought about considerable improvement on its glucose sensitivity. We tried to introduce functional groups onto an anthracene ring in order to improve the dies' fluorescence properties. Acetyl or carboxyl substitution on anthracene contributed to shift the fluorescence wavelength into the more visible range (red-shift) and a divergence of wavelength between an excitation peak and an emission peak. This improvement is advantageous to the design of an optical detection system. Furthermore, single arm immobilization to this carboxyl group, thus linking directly to the fluorophore led to a 3rd generation sensor, an immobilized bis-phenylboronate/single-arm type, that was twice as sensitive as that of the 2nd generation sensor, presumably due to increased mobility of the dye moiety. The results of our study advance closer toward a clinically useful continuous fluorescent glucose sensor.

Anthracenes↗
PubMed2001

A hydrogen-bonding receptor that binds cationic monosaccharides with high affinity in methanol.

A dicarboxylate host (1) binds cationic monosaccharides such as D-glucosamine HCl (2), D-galactosamine-HCl (3), and D-mannosamine-HCl (4) with high affinity (K1 = 8.0 x 10(4)-2.0 x 10(5) M(-1)) in methanol. In circular dichroism (CD) spectroscopy a positive exciton-coupling band was observed near 290 nm; this indicates that the saccharides are recognized by multiple point interactions. Since the corresponding neutral monosaccharides are not significantly bound, one may conclude that complex formation is primarily due to the electrostatic interaction between NH3+ in the guest and one carboxylate in the host and secondarily due to hydrogen-bonding interactions of OH groups with the other carboxylate and/or nitrogen bases. Molar ratio plots and Job plots indicate that host 1 and cationic monosaccharide guests form CD-active, pseudo-cyclic 1:1 complexes at low guest concentration followed by the formation of CD-silent, acyclic 1:2 1-saccharide complexes at high guest concentration. The possible binding modes are discussed in detail on the basis of molecular mechanics calculations and chemical shift changes in 1H NMR spectra. The results of competition experiments with several cationic reference compounds bearing fewer OH groups than 2-4 are consistent with the proposed binding model. Thus, the present study is a rare example of saccharide recognition in a protic solvent, where in general, hydrogen-bonding interactions are rarely useful because of strong solvation energy. These are apparently the strongest saccharide complexes involving noncovalent interactions between host and guest. We believe that the findings are significant as a milestone toward development of new saccharide recognition systems ultimately useful in aqueous solution.

Carrier Proteins↗
PubMed2001

Rational design of a sugar-appended porphyrin gelator that is forced to assemble into a one-dimensional aggregate.

[structure--see text] As an attempt to rationally design organogelators, an amphiphilic porphyrin bearing four beta-D-galactopyranoside groups at its periphery was synthesized. This compound tends to aggregate in a one-dimensional direction, resulting in very robust gels in DMF/alcohol mixed solvents. Spectroscopic studies and electron-micrographic observations support the view that the pi-pi stacking interaction among porphyrin moieties and the hydrogen-bonding interaction among sugar moieties operate synergistically to give rise to a stable one-dimensional aggregate structure indispensable for gel formation.

Journal Article↗
PubMed2001

First successful molecular design of an artificial Lewis oligosaccharide binding system utilizing positive homotropic allosterism.

We have designed phenylboronic acid group appended Ce(IV) bis(porphyrinate) double decker 1 and meso-meso linked porphyrin 2, useful for the allosteric binding of biologically important saccharides, Lewis oligosaccharides. Compound 1 binds Lewis oligosaccharides in aqueous media because of the boronic acid-diol interaction, but the complexation event can occur only above the critical concentrations because of the sigmoidal [oligosaccharide] versus [complex] isotherm. Compound 1 has a sufficiently high affinity with Lewis oligosaccharides (K = 10(5)-10(6) M(-2)) with Hill coefficients n of 1.8-2.0, and Lewis(X) series and Lewis(a) series give opposite, symmetrical CD spectra. This is the first example of efficient binding of Lewis oligosaccharides to the artificial receptor, which has become possible by positive homotropic allosterism.

Carbohydrate Conformation↗
PubMed2001

Sugar-integrated gelators of organic solvents.

Some methyl 4,6-O-benzylidene monosaccharides can act as strong low molecular weight gelators for various organic solvents. As they are accessible in a variety of homologues, each with a unique molecular architecture, they can be used for systematic studies of gelation phenomena. Structural details of their hydrogen-bond-based fiber network in the gel phase can be resolved by small angle X-ray scattering (SAXS). Analysis of the molecular arrangement in a single crystal can be a valuable tool for the prediction of gelation ability presupposing that the elongated shape of the gel fibers arises from an anisotropic assembly of the gelator molecules into one-dimensional aggregates. It is found that some derivatives act as "supergelators", which can gelate hydrocarbon solvents with 0.03-0.05 wt%. The recent results emerging from these investigations will be outlined in this article.

Journal Article↗
PubMed2001

Helical ribbon aggregate composed of a crown-appended cholesterol derivative which acts as an amphiphilic gelator of organic solvents and as a template for chiral silica transcription.

New crown-appended cholesterol-based organogelator 1, which has two cholesterol skeletons as a chiral aggregate-forming site, two amino groups as an acidic proton-binding site, and one crown moiety as a cation-binding site, was synthesized, and the gelation ability was evaluated in organic solvents. It can gelate acetic acid, acetonitrile, acetone, ethanol, 1-butanol, 1-hexanol, DMSO, and DMF under 1.0 wt %, indicating that 1 acts as a versatile gelator of various organic solvents. To characterize the aggregation mode in the organogel system, we observed a CD spectrum of the acetic acid gel 1. In the CD spectrum, the lambda(theta)=0 value appears at 353 nm, which is the same as the absorption maximum lambda(max) = 353 nm. The positive sign for the first Cotton effect indicates that the dipole moments of azobenzene chromophores tend to orient in a clockwise direction. Very surprisingly, the TEM images of the 1 + acetic acid gel resulted in the helical ribbon and the tubular structures. Sol-gel polymerization of tetraethoxysilane was carried out using 1 in the gel phase. The silica obtained from the 1 + acetic acid gel showed the helical ribbon with 1700-1800-nm pitches and the tubular structure of the silica with approximately 560-nm outer diameter. As far as can be recognized, all the helicity possesses a right-handed helical motif. Since the exciton-coupling band of the organogel also shows R (right-handed) helicity, we consider that a microscopic helicity is reflected by a macroscopic helicity.

Journal Article↗
PubMed2001

Ring closure of carbon nanotubes.

Lightly etched single-walled carbon nanotubes are chemically reacted to form rings. The rings appear to be fully closed as opposed to open coils, as ring-opening reactions did not change the structure of the observed rings. The average diameter of the rings was 540 nanometers with a narrow size distribution. The nanotubes in solution were modeled as wormlike polymer chains, yielding a persistence length of 800 nanometers. Nanotubes shorter than this length behave stiffly and stay nearly straight in solution. However, nanotubes longer than the Kuhn segment length of 1600 nanometers undergo considerable thermal fluctuation, suggesting a greater flexibility of these materials than is generally assumed.

Journal Article↗
PubMed2001

A self-assembled homooxacalix[3]arene-based dimeric capsule constructed by a Pd(II)-pyridine interaction which shows a novel chiral twisting motion in response to guest inclusion.

A capsule-like molecule was constructed by dimerization of pyridine-containing homooxacalix[3]aryl esters utilizing a Pd(II)-pyridine interaction when Li(+) ions were bound to the ionophoric lower rims. (1)H NMR spectral studies showed that the self-assembled molecular capsule 3b.(Li(+))(2) has a highly symmetrical D(3)(h)-structure. It was also found that this self-assembled molecular system can form capsular structures in the presence of Na(+) or ammonium (RNH(3)(+)) ions. Very interestingly, these molecular capsules are twisted into triply bridged helical structures, and chiral RNH(3)(+) guests included in the cavity induce a change in the (P) versus (M) ratio, resulting in high chiral induction ( approximately 70%). These results indicate that the self-assembled molecular capsule 3b has a novel chiral factor in which the (P) versus (M) equilibrium is readily controllable by the inclusion of chiral guest molecules.

Journal Article↗
PubMed2001

Further evidence for the gelation ability-structure correlation in sugar-based gelators.

Eight methyl glycosides of 4,6-O-benzylidene derivatives of the monosaccharides D-glucose, D-mannose, D-allose and D-altrose were synthesized to systematically study the effect of small configurational changes on the ability to gelate organic solvents. Among the beta anomers, only the D-mannose glycoside exhibits a strong gelation ability, whereas in the alpha-series the D-glucose and D-mannose derivatives act as versatile gelators. Also, as a general rule we found that the beta anomers possess a higher ability to gelate solvents than the alpha anomers. The gelation properties are discussed on the basis of SAXS, FTIR, differential scanning calorimetric (DSC) measurements and scanning electron microscopy (SEM) observations. The temperature-dependent SAXS measurements were carried out to elucidate the sol-gel transition temperature. The present study emphasizes that the saccharide family provides, not only valuable information of the structural requirements for the design of new gelators, but also for molecular assembly systems in general.

Carbohydrate Conformation↗
PubMed2001

Creation of novel chiral cryptophanes by a self-assembling method utilizing a pyridyl-Pd(II) interaction.

[structure: see text]. This Letter demonstrates the molecular design of novel self-assembled chiral cryptophanes. Mediated by square-planar Pd(II) complexes, racemic pyridyl cyclotriveratrylene derivative rac-2 self-assembles into mixtures of racemic chiral cryptophanes and meso cryptophanes (1), which interconvert with each other, and the rates are remarkably enhanced by the addition of a slight excess of rac-2. On the other hand, optically resolved P-2 or M-2 self-assembles into the chiral cryptophane as the only product.

Journal Article↗
PubMed2001

Metal-mediated self-assembly of pyridylcalixarenes: prevention of intramolecular metal chelation is essential in constructing molecular capsules.

To construct calixarene-based molecular capsules utilizing the pyridyl-Pd(II) interaction, reactions of cone-pyridylcalix[4]arene 3, cone-pyridylcalix[5]arene 13, and cone-pyridylcalix[4]arene bis-crown 16 with square-planar Pd(II) complex 7 were investigated. Because of the coexistence of intermolecular binding and chelate-forming intramolecular binding, the reactions of cone-pyridylcalix[4]arene 3 or cone-pyridylcalix[5]arene 13 with cis-Pd(II) complex 7 yield complicated, structure-unknown oligomers. The short dioxyethylene bridges on the lower rim of pyridylcalix[4]arene bis-crown 16 rigidify the cone conformation and thus prohibit 16 from the intramolecular binding with a metal component. Thus, two cone-tetrapyridylcalix[4]arene bis-crown 16 and four cis-Pd(II) complex molecules self-assemble into molecular capsules that exist as a parallel/antiparallel conformer mixture in a nearly 1:1 ratio. The results demonstrated that to prevent entropically favorable intramolecular binding is essential is constructing higher capsule-like structures with calixarene building blocks by self-assembling.

Journal Article↗
PubMed2001

Polysaccharide-polynucleotide complexes (IV): antihydrolysis effect of the schizophyllan/poly(C) complex and the complex dissociation induced by amines.

Polymer complexes formed by schizophyllan and poly(C) showed a unique antihydrolysis effect when poly(C) was subjected to hydrolysis under basic conditions. The complexation reduced the hydrolysis rate to 80% of the control (i.e., poly(C) itself). However, when we added oligoamines with the intention of catalyzing the hydrolysis, the oligoamines induced dissociation of the complex instead of acceleration of the hydrolysis.

Amines↗
PubMed2001

Molecular design of artificial molecular and ion recognition systems with allosteric guest responses.

Positive or negative allosterisms are ubiquitously seen in nature where the biological events must be efficiently regulated in response to chemical or physical signals from the outside world. The biomimetic design of such allosteric systems is of great significance in order to regulate the complexation ability or the catalytic activity of artificial receptors according to an allosteric manner. Furthermore, the methodology is very useful to amplify and convert weak chemical or physical signals into other signals which are convenient for us to read out and record. Allosteric systems are classified into four different categories: positive heterotropic, negative heterotropic, positive homotropic, and negative homotropic. In this Account, we account for our artificial allosteric systems and discuss the basic concept for molecular design of such allosteric systems and what kinds of new functions come out of such dynamic systems.

Allosteric Site↗
PubMed2001

Positive allosteric systems designed on dynamic supramolecular scaffolds: toward switching and amplification of guest affinity and selectivity.

Positive homotropic allosterism appears in important information transduction processes where chemical and physical signals are efficiently amplified. The phenomena are ubiquitous in nature, but the general methodology for the design of such allosteric systems is not yet established in an artificial system. This account reviews such artificial receptors that can bind guest ions and molecules in a positive allosteric manner and discusses what kinds of factors are indispensable as scaffolds in the design of this novel class of allosteric systems and what common factors are needed to realize the cooperativity. It has been shown that the scaffolds are mostly dynamic and are skillfully combined with the molecular recognition systems so that the subsequent guest binding can occur more favorably than the first guest binding. In addition, it has been suggested that positive homotropic allosterism can be utilized as a new strategy to attain high guest selectivity and guest affinity which cannot be attained by conventional 1:1-type guest binding.

Allosteric Site↗