Rapid detection of protein phosphatase activity using Zn(II)-coordinated gold nanosensors based on His-tagged phosphopeptides.

We report a rapid colorimetric assay to detect protein phosphatase (PP) activity based on the controlled assembly and disassembly of gold nanoparticles (AuNPs) via Zn(II)-specific coordination in the presence of His6-tagged phosphopeptides. Among divalent metal ions including Ni(II), Cu(II), Co(II), Mg(II), Mn(II), and Zn(II), only Zn(II) triggered a strong association between phosphopeptides with hexahistidine at a single end and nitrilotriacetic acid (NTA)-modified AuNPs (21.3 nm in core diameter), leading to the self-assembly of AuNPs and consequently changes in color of the AuNP solution. In contrast, unphosphorylated peptides and His6-deficient phosphopeptides did not change the color of the AuNP solution. As a result, protein phosphatase 1 (PP1) activity and its inhibition were easily quantified with high sensitivity by determining the extinction ratio (E520/E700) of colloidal AuNPs. Most importantly, this method was capable of detecting protein phosphatase 2A (PP2A) activity in immunoprecipitated plant extracts. Because PPs play pivotal roles in mediating diverse signal transduction pathways as primary effectors of protein dephosphorylation, we anticipate that our method will be applied as a rapid format method to analyze the activities of various PPs and their inhibition.

Use of complementary and alternative medicine among Korean cancer patients.

BACKGROUND: Complementary and alternative medicine (CAM) is now being increasingly used among cancer patients. The objectives of our study were to assess the prevalence, types, cost, subjective effects, and side effects of CAM use, reasons for CAM use, characteristics of CAM users compared to those of nonusers, and patients' expectations of doctors regarding their CAM use among Korean cancer patients at a single cancer center. METHODS: From April to August, 2003, we interviewed 186 cancer patients hospitalized in the Korea Cancer Center Hospital using a structured questionnaire, and analyzed the data. RESULTS: 78.5% of experimental subjects (146 patients) had been treated with at least one type of CAM, in addition to conventional Western treatment, with a mean monthly cost of 1,380,000 Won/person (approximately, 1,100 U.S. dollars on July, 2004). The most prevalent types of CAM used by these patients included medicinal mushrooms (67.1%), herbs (54.1%), vegetable diets (50.6%), and ginseng (46.5%). The main reported reasons for the use of CAM in addition to conventional medicine were nutritional support (19.1%) and physical strengthening (17.8%). 5% of CAM users experienced side effects. The younger and more educated the patients were, the more likely they were to employ CAM. 66% of CAM users wanted to discuss CAM techniques with their doctors. CONCLUSION: More than two-thirds of cancer patients used various kinds of CAM, incurring considerable costs. Therefore, in order to help patients make informed decisions, medical society should be open to communication with patients. Not only the scientific aspects, but also the economic aspects of CAM usage should be examined more thoroughly, in order to ensure proper distribution of medical resources.