A mass spectrometry screening method for antiaggregatory activity of proteins covalently modified by combinatorial library members: application to sickle hemoglobin

A homogeneous assay, based on electrospray mass spectrometry, is described for identifying compounds in a combinatorial library that covalently modify a protein and thereby enhance its solubility. The technique is based on measuring the distribution of modified proteins in the supernatant versus aggregate. Compounds having the greatest anti-aggregatory activity are those with the highest supernatant/aggregate ratio. Mass is used as a marker to identify which covalent modifier in the library is involved. An exploratory study is presented which demonstrates that the antisickling activity of a family of isothiocyanates, as measured by the standard C(sat) assay, correlates well (r(2) = 0.98) with the mass spectrometry analysis of the supernatant/aggregate distribution. The technique has potential for screening libraries capable of covalently modifying other proteins of clinical interest, e.g., Alzheimer's, Huntington's, and various prion related diseases.     

Nonequilibrium phase transitions into absorbing states

Systems with absorbing (trapped) states may exhibit a nonequilibrium phase transition from a noise-free inactive phase into an ever-lasting active phase. We briefly review the absorbing critical phenomena and universality classes, and discuss over the controversial issues on the pair contact process with diffusion (PCPD). Two different approaches are proposed to clarify its universality issue, which unveil strong evidences that the PCPD belongs to a new universality class other than the directed percolation class.     

Preparation and characterization of Pt-supported porous graphite nanofibers

In this work, porous graphite nanofibers (PGNFs) were manufactured as promising catalyst supporter by a physical activation method for direct methanol fuel cells, and Pt nanoparticles were loaded on the PGNFs in order to prepare electrode materials by a chemical reduction method. The pore structures of the Pt/PGNFs were analyzed by N₂ adsorption isotherms at 77 K. Electrocatalytic activities of final products were investigated by voltammetry and conductivity measurements in a 1.0 M CH₃OH/0.5 M H₂SO₄. As a result, electrocatalytic activities of Pt/PGNFs were increased in the presence of Pt particles on the PGNFs and with increasing the specific surface area of the carbons.     

Improved cycle sequencing of GC-rich DNA template

Even when DNA sequencing of purified DNA template failed under the optimal condition, it can be generally contributed to high GC content. GC-rich region of template causes a secondary structure to produce shorter readable sequence. To solve this problem, the sequencing reaction was modified by using dimethyl sulfoxide (DMSO). It was found that 5% (v/v) of DMSO in the reaction mixture recovers sequencing signal intensity with reduced frequency of ambiguous bases. When DMSO was added to sequencing reaction of DNA template with normal GC content, it did not show any adverse effect. Sequencing accuracy and unambiguous base frequency were significantly improved at concentration of 2% to 5% (v/v) DMSO in GC-rich DNA template. DMSO has been empirically introduced to enhance the efficiency of PCR in GC-rich templates. However, the underlying mechanism of improved cycle sequencing by DMSO is unknown. Thus, cycle sequencing reaction was remodified with other additives such as N-methyl imidazole, N-methyl2-pyrrolidone, N-methyl-2-pyridone and glycerol, possessing the similar chemical properties as DMSO. Most of methyl nitrogen ring-containing chemicals did not improve sequencing accuracy, whereas only glycerol mimicked the positive effect of DMSO by the same extent. In the present study, we suggest that the treatment of DMSO improve cycle sequencing by the alteration of structural conformation of GC-rich DNA template.     

The Macromolecular Route to Chiral Amplification

Cooperative phenomena, described by one-dimensional statistical physical methods, are observed between the enantiomeric characteristics of monomeric materials and the polymers they produce. The effect of minute energies associated with this amplified chirality, although currently not interpretable, can be easily measured. Nonlinear relationships between enantiomeric excess or enantiomeric content and polymer properties may offer the possibility of developing chiral catalysts and chiral chromatographic materials in which the burden of large enantiomeric excess or content may be considerably alleviated. New approaches to information and sensor technology may become possible.     

Low Rank Approximation of a Hankel Matrix by Structured Total Least Norm

The structure preserving rank reduction problem arises in many important applications. The singular value decomposition (SVD), while giving the closest low rank approximation to a given matrix in matrix L ₂ norm and Frobenius norm, may not be appropriate for these applications since it does not preserve the given structure. We present a new method for structure preserving low rank approximation of a matrix, which is based on Structured Total Least Norm (STLN). The STLN is an efficient method for obtaining an approximate solution to an overdetermined linear system AX B, preserving the given linear structure in the perturbation [E F] such that (A + E)X = B + F. The approximate solution can be obtained to minimize the perturbation [E F] in the L _p norm, where p = 1, 2, or . An algorithm is described for Hankel structure preserving low rank approximation using STLN with L _p norm. Computational results are presented, which show performances of the STLN based method for L ₁ and L ₂ norms for reduced rank approximation for Hankel matrices.     

红外光谱法快速测定润滑油添加剂

利用ＰＥ－ＦＴＩＲ红外光谱仪及ＰＥ公司“Ｑｕａｎｔ”计算机软件,测定润滑油添加剂单剂与复合剂含量,实际测定了１５Ｗ／４０ＳＥ、１５／３０ ＳＥ／ＣＤ、１５／Ｗ４０ＣＤ、１５Ｗ／３０ＣＣ油品试样。测量范围为０．２％￣９０％,测定相对误差小于１０％。     

冻干过程中升华界面温度测量方法的研究

压力测温技术是基于在平衡状态下,冰晶温度与其饱和蒸汽压为单值函数这一基本规律,在升华干燥过程中,突然中断从冻干室流向冷阱的水蒸汽流,通过测量冻干室内压力回升情况去推算升华界面温度的一种非接触式测温方法。与热电偶或热敏电阻测温相比,压力测温技术即不破坏冻干样品的结构,又能够较为准确地反应出移动升华界面的温度,并能判断升华干燥过程终点。文中分析了升华界面温度测量的意义与困难,建立了压力测温技术的数学模型与分析方法,并通过实验研究了压力测温技术。     

Compatibilizing effect of polyarylate-polystyrene block copolymer in polyarylate/polystyrene blends

The compatibilizing effect of polyarylate-polystyrene (PAR-PS) block copolymer prepared from macroazo initiator was examined in polyarylate/polystyrene blends from the view-points of morphology, density, and thermal, mechanical, and rheological properties. PARPS block copolymer enhanced the mutual dissolution of the homopolymers. Reduced dispersed-domain size and increased density showed the efficiency of the block copolymer as a compatibilizing agent. Results from mechanical and rheological properties could also be explained by the compatibilizing effect of PAR-PS block copolymer in the blends. © 1994 John Wiley & Sons, Inc.     

Policies and criteria on accreditation of testing laboratories in Korea

Policies and criteria for the accreditation of testing laboratories in Korea are reviewed according to the laws and regulations within the organizational framework. According to the Weights and Measures Act, the administrator of Korean Industrial Advancement Administration (KIAA) may accredit qualified testing laboratories in Korea. Criteria, procedures, and surveillance of accredited laboratories are specified in the Enforcement Regulation of the Weights and Measures Act drawn up by the Ministry of Trade, Industry, and Energy. Further detailed accreditation criteria and processes are prescribed in the Operation Guideline for the Accreditation of Testing Laboratories prepared by the KIAA. The Korean Laboratory Accreditation Scheme (KOLAS) of the KIAA is the authorized representative institution for the accreditation of testing laboratories in compliance with the ISO Guides 25/58 and the Operation Guideline for the Accreditation of Testing Laboratories. Finally, the current status of accredited laboratories in Korea is briefly described.