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Wilson GA, Cheyne K, Ramrakha S, Ambler A, Tan GS, Caspi A, Williams B, Sugden K, Houts R, Niederer RL, Wong TY, Moffitt TE, Poulton R. Are macular drusen in midlife a marker of accelerated biological ageing? Clin Exp Optom 2023; 106:41-46. [PMID: 34902293 DOI: 10.1080/08164622.2021.2012428] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 10/04/2021] [Accepted: 11/15/2021] [Indexed: 01/13/2023] Open
Abstract
CLINICAL RELEVANCE Macular drusen are associated with age-related maculopathy but are not an ocular manifestation or biomarker of systemic ageing. BACKGROUND Macular drusen are the first sign of age-related maculopathy, an eye disease for which age is the strongest risk factor. The aim of this cohort study was to investigate whether macular drusen in midlife - a sign of the earliest stages of age-related macular degeneration (AMD) - are associated with accelerated biological ageing more generally. METHODS Members of the long-running Dunedin Multidisciplinary Health and Development Study (hereafter the Dunedin Study, n = 1037) underwent retinal photography at their most recent assessment at the age of 45 years. Images were graded for the presence of AMD using a simplified scale from the Age-Related Eye Disease Study (AREDS). Accelerated ageing was assessed by (i) a measure of Pace of Ageing defined from a combination of clinical and serum biomarkers obtained at ages 26, 32, 38, and 45 years and (ii) Facial Ageing, defined from photographs obtained at age 38 and 45 years. RESULTS Of the 938 participants who participated at the age 45 assessments, 834 had gradable retinal photographs, and of these 165 (19.8%) had macular drusen. There was no significant difference in Pace of Ageing (p = .743) or Facial Ageing (p = .945) among participants with and without macular drusen. CONCLUSIONS In this representative general population sample, macular drusen in midlife were not associated with accelerated ageing. Future studies tracking longitudinal changes in drusen number and severity at older ages may reveal whether drusen are a biomarker of accelerated ageing.
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Affiliation(s)
- Graham A Wilson
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand
| | - Kirsten Cheyne
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand
| | - Sandhya Ramrakha
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand
| | - Antony Ambler
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand
| | - Gavin Sw Tan
- Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Medical School, National University of Singapore, Singapore
| | - Avshalom Caspi
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina, USA
| | - Ben Williams
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina, USA
| | - Karen Sugden
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina, USA
| | - Renate Houts
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina, USA
| | - Rachael L Niederer
- Department of Ophthalmology, University of Auckland, Auckland, New Zealand
| | - Tien Yin Wong
- Singapore Eye Research Institute, Singapore National Eye Centre, Duke-NUS Medical School, National University of Singapore, Singapore
| | - Terrie E Moffitt
- Department of Psychology and Neuroscience, Duke University, Durham, North Carolina, USA
| | - Richie Poulton
- Dunedin Multidisciplinary Health and Development Research Unit, Department of Psychology, University of Otago, Dunedin, New Zealand
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2
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Chua J, Ke M, Tan B, Gan ATL, Lim LS, Tan GS, Lee SY, Wong E, Schmetterer L, Cheung N. Association of macular and choroidal perfusion with long-term visual outcomes after macula-off rhegmatogenous retinal detachment. Br J Ophthalmol 2021; 106:1258-1263. [PMID: 33827859 DOI: 10.1136/bjophthalmol-2021-318907] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2021] [Revised: 02/27/2021] [Accepted: 03/13/2021] [Indexed: 01/07/2023]
Abstract
BACKGROUND/AIMS To examine the relationship between macular perfusion, as assessed using optical coherence tomography angiography (OCTA), and long-term visual outcome after surgical repair of macula-off rhegmatogenous retinal detachment (RRD). METHODS A prospective study of 29 patients who had undergone successful surgical repair of macula-off RRD. OCTA imaging was performed at month 3 and repeated at months 6 and 12 after surgery. Associations between OCTA parameters including, foveal avascular zone (FAZ) area, vessel density (VD) in the superficial capillary plexus (SCP) and deep capillary plexus (DCP), choriocapillaris flow deficit features and logMAR best-corrected visual acuity (VA) were assessed using a random intercept hybrid linear mixed model. RESULTS Over the 1-year follow-up, VA improved (0.025 logMAR/ month, 95% CI 0.015 to 0.035) and FAZ area decreased (-0.020 mm2/month, 95% CI -0.032 to -0.007). Better VA after surgery was significantly associated with denser superficial VD (β=0.079, 95% CI 0.026 to 0.131), lower number of choriocapillaris flow deficits (β=-0.087, 95% CI -0.154 to -0.021) and larger average size of choriocapillaris flow deficits (β=0.085, 95% CI 0.022 to 0.147), after adjusting for baseline VA, types of surgery and other factors. CONCLUSIONS OCTA measures of vascular perfusion in the macula may provide new pathophysiological insights and prognostic information related to macula-off RRD.
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Affiliation(s)
- Jacqueline Chua
- Singapore Eye Research Institute, Singapore National Eye Centre, Singapore.,Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore.,SERI-NTU Advanced Ocular Engineering (STANCE), Singapore
| | - Mengyuan Ke
- SERI-NTU Advanced Ocular Engineering (STANCE), Singapore
| | - Bingyao Tan
- SERI-NTU Advanced Ocular Engineering (STANCE), Singapore.,Institute for Health Technologies, Nanyang Technological University, Singapore
| | | | - Laurence S Lim
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore
| | - Gavin Sw Tan
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore
| | - Shu Yen Lee
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore
| | - Edmund Wong
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore
| | - Leopold Schmetterer
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore.,SERI-NTU Advanced Ocular Engineering (STANCE), Singapore.,Institute for Health Technologies, Nanyang Technological University, Singapore.,Department of Clinical Pharmacology, Medical University Vienna, Vienna, Austria.,Center for Medical Physics and Biomedical Engineering, Medical University Vienna, Vienna, Austria.,Institute of Molecular and Clinical Ophthalmology, Basel, Switzerland
| | - Ning Cheung
- Ophthalmology and Visual Sciences Academic Clinical Program, Duke-National University of Singapore Medical School, Singapore
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Tan ACS, Tan GS, Denniston AK, Keane PA, Ang M, Milea D, Chakravarthy U, Cheung CMG. An overview of the clinical applications of optical coherence tomography angiography. Eye (Lond) 2018; 32:262-286. [PMID: 28885606 PMCID: PMC5811700 DOI: 10.1038/eye.2017.181] [Citation(s) in RCA: 117] [Impact Index Per Article: 19.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2017] [Accepted: 07/15/2017] [Indexed: 12/15/2022] Open
Abstract
Optical coherence tomography angiography (OCTA) has emerged as a novel, non-invasive imaging modality that allows the detailed study of flow within the vascular structures of the eye. Compared to conventional dye angiography, OCTA can produce more detailed, higher resolution images of the vasculature without the added risk of dye injection. In our review, we discuss the advantages and disadvantages of this new technology in comparison to conventional dye angiography. We provide an overview of the current OCTA technology available, compare the various commercial OCTA machines technical specifications and discuss some future software improvements. An approach to the interpretation of OCTA images by correlating images to other multimodal imaging with attention to identifying potential artefacts will be outlined and may be useful to ophthalmologists, particularly those who are currently still unfamiliar with this new technology. This review is based on a search of peer-reviewed published papers relevant to OCTA according to our current knowledge, up to January 2017, available on the PubMed database. Currently, many of the published studies have focused on OCTA imaging of the retina, in particular, the use of OCTA in the diagnosis and management of common retinal diseases such as age-related macular degeneration and retinal vascular diseases. In addition, we describe clinical applications for OCTA imaging in inflammatory diseases, optic nerve diseases and anterior segment diseases. This review is based on both the current literature and the clinical experience of our individual authors, with an emphasis on the clinical applications of this imaging technology.
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Affiliation(s)
- A C S Tan
- Singapore National Eye Center, Singapore Eye Research Institute, Singapore, Singapore
- Singapore Eye Research Institute, Singapore Singapore
- Duke-NUS Medical School, Singapore, Singapore
| | - G S Tan
- Singapore National Eye Center, Singapore Eye Research Institute, Singapore, Singapore
- Singapore Eye Research Institute, Singapore Singapore
- Duke-NUS Medical School, Singapore, Singapore
| | - A K Denniston
- Department of Ophthalmology, University Hospitals of Birmingham NHS Foundation Trust, Birmingham, UK
- Academic Unit of Ophthalmology, Institute of Inflammation and Ageing, University of Birmingham, Birmingham, UK
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
| | - P A Keane
- National Institute for Health Research (NIHR) Biomedical Research Centre at Moorfields Eye Hospital NHS Foundation Trust and UCL Institute of Ophthalmology, London, UK
| | - M Ang
- Singapore National Eye Center, Singapore Eye Research Institute, Singapore, Singapore
- Singapore Eye Research Institute, Singapore Singapore
- Duke-NUS Medical School, Singapore, Singapore
| | - D Milea
- Singapore National Eye Center, Singapore Eye Research Institute, Singapore, Singapore
- Singapore Eye Research Institute, Singapore Singapore
- Duke-NUS Medical School, Singapore, Singapore
| | - U Chakravarthy
- Department of Ophthalmology, Queen's University of Belfast, Royal Victoria Hospital, Belfast, Northern Ireland
| | - C M G Cheung
- Singapore National Eye Center, Singapore Eye Research Institute, Singapore, Singapore
- Singapore Eye Research Institute, Singapore Singapore
- Duke-NUS Medical School, Singapore, Singapore
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Ting DS, Lu VHJ, Tan GS, Wong EY. A surprising visual improvement following a prolonged 5-month retained subfoveal perfluorocarbon liquid. Int J Ophthalmol 2016; 9:1079-81. [PMID: 27500121 DOI: 10.18240/ijo.2016.07.24] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2015] [Accepted: 10/28/2015] [Indexed: 11/23/2022] Open
Affiliation(s)
- Daniel Sw Ting
- Singapore National Eye Center, 11 Third Hospital Avenue, 168751, Singapore
| | - Vicky Hsin-Ju Lu
- Singapore National Eye Center, 11 Third Hospital Avenue, 168751, Singapore
| | - Gavin Sw Tan
- Singapore National Eye Center, 11 Third Hospital Avenue, 168751, Singapore
| | - Edmund Ym Wong
- Singapore National Eye Center, 11 Third Hospital Avenue, 168751, Singapore
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Ramli N, Chai SM, Tan GS, Husain R, Hoh ST, Ho CL, Aung T. Efficacy of medical therapy in the initial management of acute primary angle closure in Asians. Eye (Lond) 2010; 24:1599-602. [DOI: 10.1038/eye.2010.92] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
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Abstract
Neurenteric cysts are rare developmental cysts lined by endodermal derived epithelium. We present the case of a 68-year-old patient presenting with seizures who was found to have an extra-axial low density lesion with associated wall calcification on CT. Aspiration and biopsy of the cyst revealed a neurenteric cyst. Such lesions of the lateral supratentorial convexity are extremely rare and calcification has not been previously reported in these intracranial cysts.
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Affiliation(s)
- G S Tan
- Department of Radiology, Kings College Hospital, Denmark Hill, London, UK
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7
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Xu PS, Tan GS, Li XZ. [A study of quality standards for fuyanke granule]. Hunan Yi Ke Da Xue Xue Bao 2000; 25:502-4. [PMID: 12212134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 04/19/2023]
Abstract
OBJECTIVE To establish the quality standards for fuyanke(FYK) granule. METHODS The phellodendron Chinese schneid, polygonum cuspidatum, sieb. et Zucc and glycyrrihza uralensis fisch in FYK granule were identified by thin-layer chromatography(TLC). The contents of berberine were determined by thin-layer chromatographic scanning(TLCs). RESULTS The average recovery rate was 97.86%, and the relative standard deviation 1.96%. CONCLUSION The method is simple, accurate and reliable.
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Affiliation(s)
- P S Xu
- Department of Pharmacy, Xiangya Hospital, Hunan Medical University, Changsha 410008
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8
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Tan GS, Dai ZY, Xu PS. [Determination of tetrandrine in human plasma by high-performance liquid chromatography]. Hunan Yi Ke Da Xue Xue Bao 2000; 25:409-10. [PMID: 12206020] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
The paper reports the determination of tetrandrine by high performance liquid chromatography (HPLC). A C18 column was used and the mobile phase was methanol-water(80:20) containing 0.03% triethylamine, detective wave was at 282 nm, the internal standard was diazepam, the sample was extracted with ether. The linear range was from 0.289 microgram.ml-1 to 4.618 micrograms.ml-1, the average recovery rate was 95.8%. The coefficients of variation of within-day and day-to-day were less than 5%. This method is simple, rapid and accurate. It can be used in biomedical sample analysis of tetrandrine.
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Affiliation(s)
- G S Tan
- Department of Pharmacy, Xiangya Hospital, Hunan Medical University, Changsha 410008
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Oon CJ, Chen WN, Lim N, Koh S, Lim GK, Leong AL, Tan GS. Hepatitis B virus variants with lamivudine-related mutations in the DNA polymerase and the 'a' epitope of the surface antigen are sensitive to ganciclovir. Antiviral Res 1999; 41:113-8. [PMID: 10320044 DOI: 10.1016/s0166-3542(99)00007-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Lamivudine is a new antiviral agent effective against hepatitis B viral (HBV) infections but can result in virus-drug resistance associated with mutations in the conserved 'YM552DD' motif of the HBV DNA polymerase. Due to their overlapping coding regions in the HBV genome, mutations in the DNA polymerase may result in substitutions in the hepatitis B surface antigen (HBsAg), albeit outside the antigenic 'a' epitope. Here we report the identification of a novel type of lamivudine-related mutations located in both the polymerase (YM552DD-->Y1552DD) and the 'a' epitope of HBsAg (Gly130-->Asp130). The same virus carried a HBsAg Gly145-->Arg145 mutation prior to therapy. Both the wild type HBV and lamivudine-related mutants with the Gly145-->Arg145 HBsAg mutation were suppressed following ganciclovir treatment, indicating a beneficial additive effect of both drugs against different forms of HBV mutants.
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Affiliation(s)
- C J Oon
- Department of Clinical Research, Singapore General Hospital, Singapore.
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10
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Tan GS, Kelly P, Kim J, Wartell RM. Comparison of cAMP receptor protein (CRP) and a cAMP-independent form of CRP by Raman spectroscopy and DNA binding. Biochemistry 1991; 30:5076-80. [PMID: 1645189 DOI: 10.1021/bi00234a034] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
The secondary structures of the cAMP receptor protein (CRP), a complex of CRP and cAMP, and a cAMP-independent receptor protein mutant (CRP*141 gln) were examined by using Raman spectroscopy. Spectra were obtained from CRP and CRP*141 gln dissolved in 0.3 M NaCl and 30 mM sodium phosphate at protein concentrations of 30-40 mg/mL. CRP and CRP.cAMP1 were compared at lower protein concentrations (10-12 mg/mL) in a solvent of 0.35 M NaCl and 20 mM sodium phosphate. Raman analysis indicates that CRP structural changes induced by one bound cAMP or by the Gly to Gln mutation at residue 141 are small. Spectra of the three CRP samples are essentially identical from 400 to 1900 cm-1. This result differs from the Raman spectroscopy study of CRP and CRP.cAMP2 cocrystals [DeGrazia et al. (1990) Biochemistry 29, 3557]. The latter work showed spectral differences between CRP and CRP.cAMP2 consistent with alterations in the protein conformation. These studies indicate that CRP and CRP.cAMP1 in solution are similar in structure and differ from CRP.cAMP2 cocrystals. Protease digestion and a DNA binding assay were also employed to characterize the wild-type and mutant proteins. CRP*141 gln exhibited the same conformational characteristics of previously reported cAMP-independent mutant proteins. It was sensitive to proteolytic attack in the absence of cAMP, or upon addition of cGMP. In the absence of cAMP, both wild-type and mutant CRPs bound noncooperatively to a 62 bp lac promoter DNA. The equilibrium constants were approximately 10(6) M-1 in 0.1 M Na+. CRP*141 gln had a 2-4-fold higher affinity for the 62 bp DNA than CRP.(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- G S Tan
- School of Biology, Georgia Institute of Technology, Atlanta 30332
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Zuo ET, Tanious FA, Wilson WD, Zon G, Tan GS, Wartell RM. Effect of base-pair sequence on the conformations and thermally induced transitions in oligodeoxyribonucleotides containing only AT base pairs. Biochemistry 1990; 29:4446-56. [PMID: 2350548 DOI: 10.1021/bi00470a027] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Tm curves, CD spectra, and kinetics results of the self-complementary DNA dodecamers d(A6T6), d(A3T3A3T3), d(A2T2A2T2A2T2), d(ATATATATATAT), and d(T6A6) demonstrate that the thermal transitions of these oligomers at low salt concentration involve a hairpin intermediate. At high salt concentrations (greater than 0.1 M Na+) only a duplex to denatured-strand transition appears to occur. The temperature and salt-concentration regions of the transitions are very sequence dependent. Alternating-type AT sequences have a lower duplex stability and a greater tendency to form hairpins than sequences containing more nonalternating AT base pairs. Of the two nonalternating sequences, d(T6A6) is significantly less stable than d(A6T6). Both oligomers have CD curves that are very similar to the unusual CD spectrum of poly(dA).poly(dT). The Raman spectra of these two oligomers are also quite similar, but at low temperature, small intensity differences in two backbone modes and three nucleoside vibrations are obtained. The hairpin to duplex transition for the AT dodecamers was examined by salt-jump kinetics measurements. The transition is faster than transitions for palindromic-sequence oligomers containing terminal GC base pairs. Stopped-flow kinetics studies indicate that the transition is second order and has a relatively low activation energy. The reaction rate increases with increasing ionic strength. These results are consistent with a three-step mechanism for the hairpin to duplex reaction: (i) fraying of the hairpin oligomers' terminal base pairs, (ii) a rate-determining bimolecular step involving formation of a cruciform-type intermediate from two hairpin oligomers with open terminal base pairs, and (iii) base-pair migration and formation in the intermediate to give the duplex.
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Affiliation(s)
- E T Zuo
- Department of Chemistry, Georgia State University, Atlanta 30303
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Abstract
Raman spectroscopy was employed to examine the secondary structure of the cAMP receptor protein (CRP). Spectra were obtained over the range 400-1900 cm-1 from solutions of CRP and from CRP-cAMP cocrystals. The spectra of CRP dissolved in 30 mM sodium phosphate and 0.15 M NaCl buffered at either pH 6 or pH 8 or dissolved in 0.15-0.2 M NaCl at protein concentrations of 5, 15, and 30 mg/mL were examined. Estimates of the secondary structure distribution were made by analyzing the amide I region of the spectra (1630-1700 cm-1). CRP secondary structure distributions were essentially the same in either pH and at all protein concentrations examined. The amide I analyses indicated a structural distribution of 44% alpha-helix, 28% beta-strand, 18% turn, and 10% undefined for CRP in solution. Raman spectra of CRP-cAMP cocrystals differed from the spectra of CRP in solution. Some differences were assigned to interfering background bands, whereas other spectral differences were attributed to changes in CRP structure. Differences in the amide III region and in the intensity at 935 cm-1 were consistent with alterations in secondary structure. Analysis of the amide I region of the CRP-cAMP cocrystal spectrum indicated a secondary structure distribution of 37% alpha-helix, 33% beta-strand, 17% turn, and 12% undefined. This result is in agreement with a published secondary structure distribution derived from X-ray analysis of CRP-cAMP cocrystals (37% alpha-helix and 36% beta-strand).(ABSTRACT TRUNCATED AT 250 WORDS)
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Affiliation(s)
- H DeGrazia
- School of Physics, Georgia Institute of Technology, Atlanta 30332
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Tan WT, Tan GS, Nather Khan IS. Solubilities of trace copper and lead species and the complexing capacity of river water in the Linggi River Basin. Environ Pollut 1988; 52:221-235. [PMID: 15092608 DOI: 10.1016/0269-7491(88)90005-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/1987] [Revised: 12/14/1987] [Accepted: 01/04/1988] [Indexed: 05/24/2023]
Abstract
Chemical forms of copper and lead in river water of the Linggi River Basin have been fractionated into ASV labile, moderately labile, slowly labile, and inert metal species, based on a previously proposed scheme. Free (hydrated) metal ions were identified by a potentiometric method using an ion selective electrode. Speciation results showed that the soluble copper and lead species occurred mainly in the moderately labile and slowly labile fractions. The speciation results are primarily interpreted in terms of organic interaction due to agricultural based and light industries, and urban discharges. The measured metal complexing capacity (MCC) of the samples reveals consistency of the results with the nature of the discharge. MCC correlates reasonably well with the value from the permanganate test on the river water. In general, the speciation pattern was found to be consistent with the findings of other workers.
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Affiliation(s)
- W T Tan
- Chemistry Department, Universiti Pertanian Malaysia 43400, Serdang, Selangor, Malaysia
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Tavares S, Thaung M, Tan GS, Novin N. Pericardial-peritoneal window for chronic pericardial effusion. Md State Med J 1981; 30:64. [PMID: 7311613] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Tan GS, Tan JS. Salmonella typhimurium gastroenteritis in children. A clinical study. J Singapore Paediatr Soc 1972; 14:97-100. [PMID: 4569413] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Tan GS, Cheng HK. Hirschsprung's disease--clinical aspects. J Singapore Paediatr Soc 1971; 13:79-84. [PMID: 5149809] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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