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시설 거주 노인의 주관적 기억장애와 인지기능변화 -1년 추적 연구
이정식 ( Jung Sik Lee ),김태학 ( Tae Hak Kim ),김한비 ( Han Bee Kim ),이우경 ( Woo Kyeong Lee ),오홍석 ( Hong Seok Oh ),박종원 ( Chong Won Park ) 한국정신병리진단분류학회 2008 精神病理學 Vol.17 No.1
Objectives: There are inconsistent results about relationships among the subjective memory complaints(SMC), objective cognitive functions and clinical implication that SMC was a significant part of Mild Cognitive Impairment(MCI) criteria associated with early stage of Alzheimer`s disease. The Authors tried to investigate change of cognitive functions in subjective memory complainers according to time interval to identify whether SMC is related with cognitive decline or not. Methods: At baseline and one-year follow-up, total 143 participants living in the asylum for the aged had a clinical examination and neuropsychological test(frontal lobe function test, CERAD-K: the Korean version of the Consortium to Establish a Registry for Alzheimer`s Disease and Digit Span Test). All of them were evaluated by four specific questions about everyday memory function. We divided the elderly into two groups(SMC+ group: 87, SMC- group: 56) and evaluated the differences in change of cognitive functions. Results: SMC+ group had lower scores on the word list recognition test than SMC- group at oneyear follow-up(MANCOVA: age and education variables were controlled). There was a statistically significant cognitive decline on the digit span-forward test at follow-up in SMC+ group. But, there was no significant difference between two groups in change of cognitive functions according to time interval. Conclusion: These results suggested that there was no difference in cognitive decline between two groups according to time interval. It is questionable and needs more investigations that SMC is a significant part of MCI criteria.
Detection of an intermediate during the unfolding process of the dimeric ketosteroid isomerase
Jang, Do Soo,Lee, Hyeong Ju,Lee, Byeongdu,Hong, Bee Hak,Cha, Hyung Jin,Yoon, Jinhwan,Lim, Kwanseop,Yoon, Ye Jeong,Kim, Jehan,Ree, Moonhor,Lee, Hee Cheon,Choi, Kwan Yong Elsevier 2006 FEBS letters Vol.580 No.17
<P><B>Abstract</B></P><P>Failure to detect the intermediate in spite of its existence often leads to the conclusion that two-state transition in the unfolding process of the protein can be justified. In contrast to the previous equilibrium unfolding experiment fitted to a two-state model by circular dichroism and fluorescence spectroscopies, an equilibrium unfolding intermediate of a dimeric ketosteroid isomerase (KSI) could be detected by small angle X-ray scattering (SAXS) and analytical ultracentrifugation. The sizes of KSI were determined to be 18.7Å in 0M urea, 17.3Å in 5.2M urea, and 25.1Å in 7M urea by SAXS. The size of KSI in 5.2M urea was significantly decreased compared with those in 0M and 7M urea, suggesting the existence of a compact intermediate. Sedimentation velocity as obtained by ultracentrifugation confirmed that KSI in 5.2M urea is distinctly different from native and fully-unfolded forms. The sizes measured by pulse field gradient nuclear magnetic resonance (NMR) spectroscopy were consistent with those obtained by SAXS. Discrepancy of equilibrium unfolding studies between size measurement methods and optical spectroscopies might be due to the failure in detecting the intermediate by optical spectroscopic methods. Further characterization of the intermediate using <SUP>1</SUP>H NMR spectroscopy and Kratky plot supported the existence of a partially-folded form of KSI which is distinct from those of native and fully-unfolded KSIs. Taken together, our results suggest that the formation of a compact intermediate should precede the association of monomers prior to the dimerization process during the folding of KSI.</P>
Contribution of a Low-Barrier Hydrogen Bond to Catalysis Is Not Significant in Ketosteroid Isomerase
Jang, Do Soo,Choi, Gildon,Cha, Hyung Jin,Shin, Sejeong,Hong, Bee Hak,Lee, Hyeong Ju,Lee, Hee Cheon,Choi, Kwan Yong Korean Society for Molecular and Cellular Biology 2015 Molecules and cells Vol.38 No.5
Low-barrier hydrogen bonds (LBHBs) have been proposed to have important influences on the enormous reaction rate increases achieved by many enzymes. ${\Delta}^5$-3-ketosteroi isomerase (KSI) catalyzes the allylic isomerization of ${\Delta}^5$-3-ketosteroid to its conjugated ${\Delta}^4$-isomers at a rate that approache the diffusion limit. Tyr14, a catalytic residue of KSI, has been hypothesized to form an LBHB with the oxyanion of a dienolate steroid intermediate generated during the catalysis. The unusual chemical shift of a proton at 16.8 ppm in the nuclear magnetic resonance spectrum has been attributed to an LBHB between Tyr14 $O{\eta}$ and C3-O of equilenin an intermediate analogue, in the active site of D38N KSI. This shift in the spectrum was not observed in Y30F/Y55F/D38N and Y30F/Y55F/Y115F/D38N mutant KSIs when each mutant was complexed with equilenin, suggesting that Tyr14 could not form LBHB with the intermediate analogue in these mutant KSIs. The crystal structure of Y30F/Y55F/Y115F/D38N-equilenin complex revealed that the distance between Tyr14 $O{\eta}$ and C3-O of the bound steroi was within a direct hydrogen bond. The conversion of LBHB to an ordinary hydrogen bond in the mutant KSI reduced the binding affinity for the steroid inhibitors by a factor of 8.1-11. In addition, the absence of LBHB reduced the catalytic activity by only a factor of 1.7-2. These results suggest that the amount of stabilization energy of the reaction intermediate provided by LBHB is small compared with that provided by an ordinary hydrogen bond in KSI.