Development of Amphipathic Antimicrobial Peptide Foldamers Based on Magainin 2 Sequence

Magainin 2 ( Mag 2 ), which is isolated from the skin of frogs, is a representative antimicrobial peptide (AMP), exerts its antimicrobial activity via microbial membrane disruption. It has been reported that both the amphipathicity and helical structure of Mag 2 play an important role in its antimicrobial activity. In this study, we revealed that the sequence of 17 amino acid residues in Mag 2 (peptide 7 ) is required to exert sufficient activity. We also designed a set of Mag 2 derivatives, based on enhancement of helicity and/or amphipathicity, by incorporation of α,α-disubstituted amino acid residues into the Mag 2 fragment, and evaluated their preferred secondary structures and their antimicrobial activities against both Gram-positive and Gram-negative bacteria. As a result, peptide 11 formed a stable helical structure in solution, and possessed potent antimicrobial activities against both Gram-positive and Gram-negative bacteria without significant cytotoxicity.     

A bucketing algorithm for the orthogonal segment intersection search problem and its practical efficiency

The orthogonal segment intersection search problem is stated as follows: given a setS ofn orthogonal segments in the plane, report all the segments ofS that intersect a given orthogonal query segment. For this problem, we propose a simple and practical algorithm based on bucketing techniques. It constructs, inO(n) time preprocessing, a search structure of sizeO(n) so that all the segments ofS intersecting a query segment can be reported inO(k) time in the average case, wherek is the number of the reported segments. The proposed algorithm as well as existing algorithms is implemented in FORTRAN, and their practical efficiencies are investigated through computational experiments. It is shown that ourO(k) search time,O(n) space, andO(n) preprocessing time algorithm is in practice the most efficient among the algorithms tested.     

Biodegradations of statistical copolymers composed of D,L‐lactide and cyclic carbonates

Syntheses and biodegradation of statistical copolymers of D ,L ‐lactide (D ,L ‐LA) with trimethylene carbonate (TMC), rac‐1‐methyltrimethylene carbonate (1‐MTMC) and 2,2‐dimethyltrimethylene carbonate (2,2‐DTMC) were investigated at various monomer ratios using SmMe(C₅Me₅)₂THF as an initiator at 80 °C for 24 h in toluene. Biodegradations of poly(D ,L ‐LA‐co‐racemo‐1‐MTMC) (95/5) and poly(D ,L ‐LA‐co‐2,2‐DTMC) (98/2) with a compost at 60 °C proceed rapidly. Enzymatic degradations of these polymers were also performed using cholesterol esterase, lipoprotein lipase and proteinase K. Only poly(D ,L ‐LA‐co‐TMC) was biodegraded with cholesterol esterase, while poly(TMC), poly(1‐MTMC), poly(2,2‐DTMC) and poly(D ,L ‐LA) were barely degraded with these enzymes. Biodegradations of poly(D ,L ‐LA‐co‐TMC) (87/13) and poly(D ,L ‐LA‐co‐racemo‐1‐MTMC) (95/5) are rapid using proteinase K. Physical properties of these copolymers were also described. © 2003 Society of Chemical Industry     

Sorption and transport of CO2 in poly(ethylene terephthalate) crystallized by sorption of high-pressure CO2

Sorption and permeation of CO₂ in poly(ethylene terephthalate) crystallized by sorption of high-pressure CO₂ were examined below 1 atm at temperatures from 15 to 65°C. A large solubility and a high permeability of CO₂ in this specimen were observed compared to poly(ethylene terephthalate) crystallized by thermal annealing to a similar degree. A large unrelaxed volume is expected to be left in the specimen after removal of high-pressure CO₂ compared to the data of other PET samples. The thermal history during the measurements up to 65°C, which causes relaxation of the specimen, was shown to decrease CO₂ solubility. On the other hand, permeation data after annealing show not only decreased permeability but also increased apparent diffusivity. The results mean a lower mobility of gases sorbed in the unrelaxed volume than that of ordinarily dissolved gases, which corresponds to the partial immobilization model.     

A retarding-grid electron spectrometer for Mössbauer spectroscopy

A new retarding-grid electron spectrometer for conversion electron Mössbauer spectroscopy has been constructed. The structure and performance of the spectrometer are described in detail. The response functions for various settings of energy resolution have been determined using the energy spectrum of a very thin ⁵⁷Co source. The best energy resolution obtained is 0.3% at 7.3 keV with a detection efficiency of $\text{1.2\%}\text{4π}$.     

A bucketing algorithm for the orthogonal segment intersection search problem and its practical efficiency

The orthogonal segment intersection search problem is stated as follows: given a setS ofn orthogonal segments in the plane, report all the segments ofS that intersect a given orthogonal query segment. For this problem, we propose a simple and practical algorithm based on bucketing techniques. It constructs, inO(n) time preprocessing, a search structure of sizeO(n) so that all the segments ofS intersecting a query segment can be reported inO(k) time in the average case, wherek is the number of the reported segments. The proposed algorithm as well as existing algorithms is implemented in FORTRAN, and their practical efficiencies are investigated through computational experiments. It is shown that ourO(k) search time,O(n) space, andO(n) preprocessing time algorithm is in practice the most efficient among the algorithms tested.Supported by the Grant-in-Aid for Scientific Research of the Ministry of Education, Science and Culture of Japan under Grant No. 62550270 (1987).     

The anodic behavior of amorphous Ni-19P alloys in different amorphous states

An amorphous Ni-19P alloy prepared by rapid quenching of white heat melt showed a higher anodic dissolution current density in 1 N HCl in comparison with the same amorphous alloy prepared by rapid quenching of red heat melt. After structural relaxation these two specimens showed the same anodic polarization curve which is located between the polarization curves of as-quenched two specimens. The thermograms of these two as-quenched specimens were different from each other, showing that the difference in the amorphous states is due to the difference in structural relaxation during preparation. The difference in anodic behavior between these two as-quenched specimens seems due to the difference in the amounts of quenched-in defects. The higher current density of the relaxed specimen in comparison with the as-quenched specimen prepared by rapid quenching of the red heat melt has been interpreted in terms of introduction of chemical heterogeneity as a result of rearrangement and regroupings of atoms in the alloy during structural relaxation. The steady state current density was fairly low in the low potential region without showing a difference between two as-quenched specimens and then increased with increasing polarization potential. The difference in the quality of as-quenched alloy specimens seemed to be masked by the formation of phosphorus-covered alloy surfaces during anodic polarization at potentials lower than about 200 mV(SCE), because of a negligibly small dissolution rate constant of phosphorus in comparison with that of nickel.     

Experimental study of the flow boiling heat transfer enhancement and pressure drop due to the bubble behavior restricted by a screen sheet

A unique method previously proposed by the authors was applied to the heat transfer augmentation in the flow boiling field. In this method a screen sheet was placed on the horizontal heated surface where bubble nucleation occurred. Generated vapor bubbles were trapped between the screen and the wall, became flat, and moved along the surface. This restricted bubble behavior caused the heat transfer enhancement. Three types of screen sheet were tested in the present experiment and the effect of the screen on the heat transfer and two‐phase flow characteristics was investigated. In two of these cases, the screen was displaced upward by the bubble nucleation. Compared with the ordinary flow boiling case, heat transfer was enhanced by a factor of 1.2 to 6 within the present experimental range. Using a simple flow model, it was made clear that the effect of the height of the displaced screen was important in evaluating the increase in pressure drop. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(4): 319–329, 2003; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/htj.10094     

Performance evaluation of candidate appointment schedules using clearing functions

This study is concerned with the problem of reducing the waiting times of outpatients. Both scheduled patients and walk-ins are included among the outpatients to reflect the typical medical environment in Japan. The consultation time of a hospital is divided into several blocks, and each scheduled patient is given the start time of a block as his or her scheduled time of the consultation as an appointment. It is assumed that all scheduled patients arrive at the hospital at their scheduled times, while walk-ins arrive randomly. A set of candidate appointment schedules is given, and the process of selecting promising schedules in terms of average waiting times is the focus of the work. To support the selection process without conducting a conventional simulation, the notion of a clearing function is adopted to evaluate each candidate schedule. The clearing function of a system gives the expected output or throughput of the system under varying levels of workload of the system. Although it is necessary to conduct exploratory experiments in advance to obtain the clearing function, the expected waiting time can be estimated by simple calculations with the aid of the clearing function. The average waiting times of four schedules in two scenarios are calculated and compared with those obtained from conventional simulations. It is revealed that the proposed procedure based on the clearing function gives acceptable estimated average values.