Chung-Ang University

About: Chung-Ang University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Population & Thin film. The organization has 13381 authors who have published 26978 publications receiving 416735 citations. The organization is also known as: CAU & Chung.

A gold-nanoparticle-based real-time colorimetric screening method for endonuclease activity and inhibition.

Abstract: Nucleic acids act as the carriers of genetic information, and most organisms contain a type of enzymes called endonucleases, which can hydrolyze the phosphodiester linkages in the nucleic acid backbone. These nucleases are important for many processes involving the replication, repair, and recombination of nucleic acids. Endonucleases such as DNA gyrase and virus integrase play key roles in biological process such as the topological altering of DNA and the insertion of proviral DNA into host chromosomal DNA. Molecules that inhibit endonucleases are therefore considered candidates for a variety of antimicrobial and antiviral drugs. As such, methods for the high-throughput screening of different nuclease inhibitors have become a central part of the drug-development process. The most widely used assays include those based on the use of chromogenic or fluorogenic substrates to produce a spectrophotometric signal. In many cases, however, it is desirable to measure the reaction between an enzyme and a well-defined nucleic acid substrate of interest, as opposed to a fluorogenic or chromogenic derivative of that substrate. Historically, endonuclease activity has been screened by viscometry, radioactive labeling, and gel electrophoresis, in addition to the more recent fluorescence-based approaches. Most of these protocols are time consuming and do not provide a measure of endonuclease activity in real time. Of these methods, only fluorescence is appreciably used for highthroughput screening, and the fluorescence-based approach has just recently been implemented. Herein, we report an operationally simple colorimetric endonuclease-inhibition assay, which enables the real-time monitoring of endonuclease activity and the simultaneous determination of the efficiencies of endonuclease inhibitors (e.g., DNA-binding molecules). The new method relies on polymeric aggregates of DNA-functionalized gold nanoparticles (DNA-AuNPs) with DNA-duplex interconnects. DNA-AuNPs have been used previously to detect DNA, proteins, metal ions, and DNA-binding molecules. Others have used gold nanoparticles and electrochemical approaches to evaluate enzymatic activity. To our knowledge, we report the first example of the use of DNA-AuNPs as colorimetric indicators to evaluate enzymatic activity and to screen enzyme inhibitors. In principle, this method can be used to screen libraries of inhibitors of endonucleases in a highthroughput fashion by using either the naked eye or a simple colorimetric reader. Probes were prepared by functionalizing two separate batches of 13-nm gold particles with two different thiolmodified oligonucleotide strands, DNA-1 (5’-CTCCCTAATAACAATTTATAACTATTCCTA-A10-SH-3’) and DNA-2 (5’-TAGGAATAGTTATAAATTGTTATTAGGGAG-A10SH-3’). These functionalized particles are denoted DNAAuNP-1 and DNA-AuNP-2. DNA-1 and DNA-2 are complementary to each other. Therefore, DNA-AuNP-1 and DNA-AuNP-2 can hybridize to form a cross-linked network of nanoparticles, which is purple in color owing to the redshifted plasmon band of the gold nanoparticles (13 nm). This red-shifting is a well-understood process and is a highly diagnostic feature of aggregate formation. These aggregates can then be used as colorimetric indicators of endonuclease activity (Scheme 1). As the endonuclease degrades the DNA-duplex interconnects, particles are released, regenerating a red color due to the dispersed nanoparticles. The color can be observed with the naked eye, or the absorbance (520 nm) can be measured by UV/Vis spectroscopy. The DNA-AuNP aggregates were used to evaluate the enzymatic activity of deoxyribonuclease (DNase) I. In a typical experiment, DNase I, at a predetermined concentration (10, 15, 20, 30, or 40 unitsmL ), was added to a solution of the aggregates. The color of the solution gradually changed from purple to red. By measuring the absorbance at 520 nm, we could quantitatively follow the nucleic acid hydrolysis catalyzed by DNase I (Figure 1 a). The reaction rate increases with increasing enzyme concentration and can be followed in real time. In addition to screening enzyme activity, one can easily use the assay to evaluate the efficiency of inhibitors of DNase I. In a typical screening experiment, DNase I (15 unitsmL ) was added to solutions of the DNA-AuNP aggregates in the presence of one of the following DNAbinding molecules (1 mm): amsacrine (AMSA), anthraquinone-2-carboxylic acid (AQ2A), 9-aminoacridine (9-AA), ellipticine (EIPT), daunorubicin (DNR), ethidium bromide (EB), or 4’,6-diamidino-2-phenylindole (DAPI). These DNAbinding molecules are known to inhibit DNase I. 12] The absorbance at 520 nm was monitored as a function of time (sample scan rate= 5 min ; Figure 1b), and the color of the solution was followed with the naked eye (Figure 2). The time [*] X. Xu, Dr. M. S. Han, [+] Prof. C. A. Mirkin Department of Chemistry and International Institute for Nanotechnology Northwestern University 2145 Sheridan Road, Evanston, IL 60208-3113 (USA) Fax: (+1)847-467-5123 E-mail: chadnano@northwestern.edu [] Current address: Department of Chemistry, Chung-Ang University Seoul 156-765, Korea [] These authors equally contributed to this work.

Sexual behaviour and dysfunction and help-seeking patterns in adults aged 40-80 years in the urban population of Asian countries.

Abstract: OBJECTIVE To study sexual activity, the prevalence of sexual dysfunction and related help-seeking behaviour among middle-aged and elderly people in Asia. SUBJECTS AND METHODS A random population survey was carried out in 2001–2002 among urban residents aged 40–80 years in China, Taiwan, South Korea, Japan, Thailand, Singapore, Malaysia, Indonesia and The Philippines, with interviews based on a standardized questionnaire covering demographic details, health, relationships, and sexual behaviours, attitudes and beliefs. An intercept method of sampling was used in all countries except Japan, where questionnaires were mailed to a sample drawn from telephone directories. Sexual dysfunction was defined as persistent sexual problems. RESULTS The questionnaire was completed by 6700 people (3350 men and 3350 women), giving a response rate of 27%. Across all countries, 82% of men and 64% of women had engaged in sexual intercourse during the year preceding the interview. Most of the respondents considered satisfactory sex an essential means of maintaining a relationship. More than 20% of men and 30% of women complained of having at least one sexual dysfunction, although there were marked variations among the countries. The sexual dysfunctions most frequently reported were early ejaculation (20%; 95% confidence interval, CI, 18–21) and erectile dysfunction (15%, 14–17) among men; and a lack of sexual interest (27%, 25–29), lubrication difficulties (24%, 22–25), and an inability to reach orgasm (23%, 22–25) among women. Of the 948 men and 992 women who were sexually active and reported sexual dysfunctions, 45% did sought no help or advice and only 21% sought medical care. CONCLUSION Men and women in Asian countries continue to show sexual interest and activity into middle age and beyond. Although sexual dysfunction is prevalent in this age group, several sociocultural and economic factors appear to be preventing individuals from seeking medical help for these problems.

Pb2BO3Cl: A Tailor-Made Polar Lead Borate Chloride with Very Strong Second Harmonic Generation

Abstract: A meticulously designed, polar, non-centrosymmetric lead borate chloride, Pb2BO3Cl, was synthesized using KBe2BO3F2 (KBBF) as a model. Single-crystal X-ray diffraction revealed that the structure of Pb2BO3Cl consists of cationic [Pb2(BO3)]+ honeycomb layers and Cl− anions. Powder second harmonic generation (SHG) measurements on graded polycrystalline Pb2BO3Cl indicated that the title compound is phase-matchable (type I) and exhibits a remarkably strong SHG response, which is approximately nine times stronger than that of potassium dihydrogen phosphate, and the largest efficiency observed in materials with structures similar to KBBF. Further characterization suggested that the compound melts congruently at high temperature and has a wide transparency window from the near-UV to the mid-IR region.