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Evaluation of a multimodal diagnostic algorithm for prediction of cognitive impairment in elderly patients with dizziness. J Neurol 2024:10.1007/s00415-024-12403-3. [PMID: 38702563 DOI: 10.1007/s00415-024-12403-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/22/2024] [Accepted: 04/23/2024] [Indexed: 05/06/2024]
Abstract
BACKGROUND The current diagnostic workup for chronic dizziness in elderly patients often neglects neuropsychological assessment, thus missing a relevant proportion of patients, who perceive dizziness as a subjective chief complaint of a concomitant cognitive impairment. This study aimed to establish risk prediction models for cognitive impairment in chronic dizzy patients based on data sources routinely collected in a dizziness center. METHODS One hundred patients (age: 74.7 ± 7.1 years, 41.0% women) with chronic dizziness were prospectively characterized by (1) neuro-otological testing, (2) quantitative gait assessment, (3) graduation of focal brain atrophy and white matter lesion load, and (4) cognitive screening (MoCA). A linear regression model was trained to predict patients' total MoCA score based on 16 clinical features derived from demographics, vestibular testing, gait analysis, and imaging scales. Additionally, we trained a binary logistic regression model on the same data sources to identify those patients with a cognitive impairment (i.e., MoCA < 25). RESULTS The linear regression model explained almost half of the variance of patients' total MoCA score (R2 = 0.49; mean absolute error: 1.7). The most important risk-predictors of cognitive impairment were age (β = - 0.75), pathological Romberg's sign (β = - 1.05), normal caloric test results (β = - 0.8), slower timed-up-and-go test (β = - 0.67), frontal (β = - 0.6) and temporal (β = - 0.54) brain atrophy. The binary classification yielded an area under the curve of 0.84 (95% CI 0.70-0.98) in distinguishing between cognitively normal and impaired patients. CONCLUSIONS The need for cognitive testing in patients with chronic dizziness can be efficiently approximated by available data sources from routine diagnostic workup in a dizziness center.
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P-66 Dizziness in Cognitive Impairment: A frequently neglected entity associated with a specific brain atrophy pattern. Clin Neurophysiol 2023. [DOI: 10.1016/j.clinph.2023.02.083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/08/2023]
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Spontaneous visual exploration during locomotion in patients with phobic postural vertigo. J Neurol 2020; 267:223-230. [PMID: 32852578 PMCID: PMC7718196 DOI: 10.1007/s00415-020-10151-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2020] [Revised: 07/23/2020] [Accepted: 08/07/2020] [Indexed: 11/29/2022]
Abstract
Background Earlier studies on stance and gait with posturographic and EMG-recordings and automatic gait analysis in patients with phobic postural vertigo (PPV) or visual height intolerance (vHI) revealed similar patterns of body stiffening with muscle co-contraction and a slow, cautious gait. Visual exploration in vHI patients was characterized by a freezing of gaze-in-space when standing and reduced horizontal eye and head movements during locomotion. Objective Based on the findings in vHI patients, the current study was performed with a focus on visual control of locomotion in patients with PPV while walking along a crowded hospital hallway. Methods Twelve patients with PPV and eleven controls were recruited. Participants wore a mobile infrared video eye-tracking system that continuously measured eye-in-head movements in the horizontal and vertical planes and head orientation and motion in the yaw, pitch, and roll planes. Visual exploration behavior of participants was recorded at the individually preferred speed for a total walking distance of 200 m. Gaze-in-space directions were determined by combining eye-in-head and head-in-space orientation. Walking speeds were calculated based on the trial duration and the total distance traversed. Participants were asked to rate their feelings of discomfort during the walk on a 4-point numeric rating scale. The examiners rated the crowdedness of the hospital hallway on a 4-point numeric rating scale. Results The major results of visual exploration behavior in patients with PPV in comparison to healthy controls were: eye and head positions were directed more downward in the vertical plane towards the ground ahead with increased frequency of large amplitude vertical orientation movements towards the destination, the end of the ground straight ahead. The self-adjusted speed of locomotion was significantly lower in PPV. Particularly those patients that reported high levels of discomfort exhibited a specific visual exploration of their horizontal surroundings. The durations of fixating targets in the visual surroundings were significantly shorter as compared to controls. Conclusion Gaze control of locomotion in patients with PPV is characterized by a preferred deviation of gaze more downward and by horizontal explorations for suitable auxiliary means for potential postural support in order to prevent impending falls. These eye movements have shorter durations of fixation as compared to healthy controls and patients with vHI. Finally, the pathological alterations in eye–head coordination during locomotion correlate with a higher level of discomfort and anxiety about falling.
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A novel pathogenic CACNA1A variant causing episodic ataxia type 2 (EA2) spectrum phenotype in four family members and a novel combined therapy. J Neurol 2020; 267:181-184. [PMID: 32910250 PMCID: PMC7718184 DOI: 10.1007/s00415-020-10190-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2020] [Revised: 08/18/2020] [Accepted: 08/26/2020] [Indexed: 11/08/2022]
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P83 Ocular-mandibular phenomenon. Clin Neurophysiol 2020. [DOI: 10.1016/j.clinph.2019.12.081] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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Approach to an experimental model of Mal de Debarquement Syndrome. J Neurol 2019; 266:74-79. [DOI: 10.1007/s00415-019-09345-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2019] [Revised: 04/23/2019] [Accepted: 04/25/2019] [Indexed: 11/29/2022]
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Association of Health Care Utilization and Handicaps in Daily Living in Vertigo Patients – Results from the DizzyReg Patient Registry. DAS GESUNDHEITSWESEN 2017. [DOI: 10.1055/s-0037-1605698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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[Fear of Heights in Primary School Children]. FORTSCHRITTE DER NEUROLOGIE-PSYCHIATRIE 2016; 84:134-6. [PMID: 27029040 DOI: 10.1055/s-0042-103424] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/22/2022]
Abstract
The life-time prevalence of visual height intolerance in adults is 28 percent, whereas in primary school children, as recently shown, it develops in 34 percent. Triggers and symptoms are similar in children and adults. A significant difference in visual height intolerance of prepubertal children compared to adults is the good prognosis with mostly spontaneous remission within a few years, possibly facilitated by repeated exposure to the triggering situations.
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Acid effect on excited Auramine-O molecular rotor relaxations in solution and adsorbed on insulin fibrils. Methods Appl Fluoresc 2015; 3:034005. [DOI: 10.1088/2050-6120/3/3/034005] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Einfluss von Höhenschwindel auf Gang und visuelle Exploration. KLIN NEUROPHYSIOL 2014. [DOI: 10.1055/s-0034-1371227] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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[Height vertigo: epidemiology and phenomenology. Results of a representative epidemiological study and a survey among members of the German Alpine Association]. MMW Fortschr Med 2013; 155 Suppl 4:104-108. [PMID: 24934063 DOI: 10.1007/s15006-013-2540-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
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[Do German articles in medical journals require a"guide to anglicisms"?]. DER NERVENARZT 2013; 84:1497-1501. [PMID: 24264644 DOI: 10.1007/s00115-013-3946-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Effective communication of scientific results depends on conceptually clear and precise language, especially with regards to the use of discipline-specific terminology. German scientific language might be more comprehensible if the overuse of anglicisms is avoided. As an example commonly used anglicisms in ten clinical studies published in Der Nervenarzt were selected, listed according to the field of application and evaluated. Adequate German terms are offered for them showing that it is possible to use German terms for most issues and facts.
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[Anglicisms necessary in the clinic? The example of vestibular and oculomotor syndromes]. DER NERVENARZT 2013; 84:1203-1206. [PMID: 24057066 DOI: 10.1007/s00115-013-3897-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
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Understanding and Controlling Organic–Inorganic Interfaces in Mesostructured Hybrid Photovoltaic Materials. J Am Chem Soc 2011; 133:10119-33. [DOI: 10.1021/ja200054z] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Abstract
The excitation of hemoproteins containing either Fe(2+) or Fe(3+) with a picosecond light pulse resulted in the bleaching and recovery of the iron absorbance bands within 6 psec. A new absorbance band also was observed whose formation and decay rate of less than 6 psec suggests that it is probably due to S(1)-->S(n) absorbance. The Soret band relaxation time is deduced to be approximately 0.5 psec whereas the free base hemoprotein does not show any of the above fast-decay characteristics. Therefore, there is a strong influence of the metal on the energy dissipation process.
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Saccular function less affected than canal function in bilateral vestibulopathy. J Neurol 2008; 255:1332-6. [DOI: 10.1007/s00415-008-0887-6] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2007] [Revised: 01/17/2008] [Accepted: 01/24/2008] [Indexed: 11/27/2022]
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Abstract
OBJECTIVE Bilateral vestibulopathy (BV) leads to a bilateral deficit of the vestibulo-ocular reflex and has various aetiologies. The main goal of this study was to determine the frequency and degree of recovery or worsening of vestibular function over time. METHODS 82 patients (59 males, 23 females; mean age at the time of diagnosis 56.3 (SD 17.6) years) were re-examined 51 (36) months after the first examination. All patients underwent a standardised neuro-ophthalmological and neuro-otological examination. Electronystagmography with bithermal caloric irrigation was analysed by measurement of the mean peak slow phase velocity (SPV) of the induced nystagmus. Patients evaluated the course of their disease in terms of balance, gait unsteadiness and health related quality of life. RESULTS Statistical analysis of the mean peak SPV of caloric induced nystagmus revealed a non-significant worsening over time (initial mean peak SPV 3.0 (3.5) degrees/s vs 2.1 (2.8) degrees/s). With respect to subgroups of aetiology, only patients with BV due to meningitis exhibited an increasing, but non-significant SPV (1.0 (1.4) degrees/s vs 1.9 (1.6) degrees/s). Vestibular outcome was independent of age, gender, time course of manifestation and severity of BV. Single analysis of all patients showed that a substantial improvement > or = 5 degrees/s occurred in two patients on both sides (idiopathic n = 1, Sjögren's syndrome n = 1) and in eight patients on one side (idiopathic n = 6, meningitis n = 1, Menière's disease n = 1). In 84% of patients there was impairment of their health related quality of life (42% slight, 24% moderate, 18% severe). Forty-three per cent of patients rated the course of their disease as stable, 28% as worsened and 29% as improved. CONCLUSIONS Our data support the view that more than 80% of patients with BV do not improve. Thus the prognosis of BV is less favourable than assumed.
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Follow-up of vestibular function in bilateral vestibulopathy. AKTUELLE NEUROLOGIE 2007. [DOI: 10.1055/s-2007-987458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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An evaluation of the effects of conservation and fishery enhancement hatcheries on wild populations of salmon. ADVANCES IN MARINE BIOLOGY 2007; 53:61-194. [PMID: 17936136 DOI: 10.1016/s0065-2881(07)53002-6] [Citation(s) in RCA: 115] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The historical, political and scientific aspects of salmon hatchery programmes designed to enhance fishery production, or to recover endangered populations, are reviewed. We start by pointing out that the establishment of hatcheries has been a political response to societal demands for harvest and conservation; given this social context, we then critically examined the levels of activity, the biological risks, and the economic analysis associated with salmon hatchery programmes. A rigorous analysis of the impacts of hatchery programmes was hindered by the lack of standardized data on release sizes and survival rates at all ecological scales, and since hatchery programme objectives are rarely defined, it was also difficult to measure their effectiveness at meeting release objectives. Debates on the genetic effects of hatchery programmes on wild fish have been dominated by whether correct management practices can reduce negative outcomes, but we noted that there has been an absence of programmatic research approaches addressing this important issue. Competitive interactions between hatchery and wild fish were observed to be complex, but studies researching approaches to reduce these interactions at all ecological scales during the entire salmon life history have been rare, and thus are not typically considered in hatchery management. Harvesting of salmon released from fishery enhancement hatcheries likely impacts vulnerable wild populations; managers have responded to this problem by mass marking hatchery fish, so that fishing effort can be directed towards hatchery populations. However, we noted that the effectiveness of this approach is dependant on accurate marking and production of hatchery fish with high survival rates, and it is not yet clear whether selective fishing will prevent overharvest of wild populations. Finally, research demonstrating disease transmission from hatchery fish to wild populations was observed to be equivocal; evidence in this area has been constrained by the lack of effective approaches to studying the fate of pathogens in the wild. We then reviewed several approaches to studying the economic consequences of hatchery activities intended to inform the social decisions surrounding programmes, but recognized that placing monetary value on conservation efforts or on hatcheries that mitigate cultural groups' loss of historical harvest opportunities may complicate these analyses. We noted that economic issues have rarely been included in decision making on hatchery programmes. We end by identifying existing major knowledge gaps, which, if filled, could contribute towards a fuller understanding of the role that hatchery programmes could play in meeting divergent goals. However, we also recognized that many management recommendations arising from such research may involve trade-offs between different risks, and that decisions about these trade-offs must occur within a social context. Hatcheries have played an important role in sustaining some highly endangered populations, and it is possible that reform of practices will lead to an increase in the number of successful programmes. However, a serious appraisal of the role of hatcheries in meeting broader needs is urgently warranted and should take place at the scientific, but more effectively, at the societal level.
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Abstract
We examined 103 patients with vestibular neuritis (VN) in a follow-up study (5.7 to 20.5 years, mean 9.8 years). Two patients (1.9%) had developed a second occurrence of VN 29 to 39 months after the first. VN affected the contralateral ear in both and caused less severe distressing vertigo and postural imbalance. Unlike Bell's palsy and sudden hearing loss, a relapse in the same ear did not occur.
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Treatment of Menière's disease with betahistine: an open trial. AKTUELLE NEUROLOGIE 2006. [DOI: 10.1055/s-2006-953061] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Phobic postural vertigo--a long-term follow-up (5 to 15 years) of 106 patients. J Neurol 2005; 252:564-9. [PMID: 15742115 DOI: 10.1007/s00415-005-0699-x] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2004] [Revised: 08/10/2004] [Accepted: 09/07/2004] [Indexed: 02/07/2023]
Abstract
One hundred and six patients diagnosed between 1987 and 1998 to have somatoform phobic postural vertigo were examined in a follow-up study with a self-evaluating questionnaire. The improvement rate after a mean follow-up time of 8.5 years (5 to 15.9 years) was 75% (27% of the patients reported a complete remission). While the majority of these patients experienced improvement or remission during the first year after assessment of diagnosis and a short-term psychotherapeutic approach, some patients also had considerable improvement even after two or more years. There was a negative correlation between the duration of the condition before assessment of the diagnosis and the improvement/regression rate. The improvement/regression rate was independent of gender, age, preceding vestibular or non-vestibular organic disorders, and the various medical, physical, or psychotherapeutic interventions. Transient relapses occurred in 47% of the improved patients once or repeatedly. The probability of developing a relapse remained constant throughout the entire follow-up. None of the patients required a revision of the initial diagnosis on the basis of the questionnaire.
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Time-resolved fluorescence depolarization measurements in mesoporous silicas: the fractal approach. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100311a001] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Catalytic structure sensitivity: the effect of pore size on the oxygen quenching of excited aromatic molecules adsorbed on silica surfaces. J Am Chem Soc 2002. [DOI: 10.1021/ja00236a041] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Surface recombination velocity measurements of cadmium sulfide single crystals immersed in electrolytes. A picosecond photoluminescence study. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100327a024] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Picosecond time-resolved luminescence study of n-cadmium selenide single crystals: comparison with cadmium sulfide. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100164a037] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Single excited vibrational level lifetimes and energy dissipation channels of large molecules in inert matrixes. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100272a047] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Picosecond dynamics of localized electrons in metal-ammonia and metal-methylamine solutions. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100593a010] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Intramolecular proton transfer as a preliminary step for proton dissociation in 2-naphthol-3,6-disulfonate. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100197a033] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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The pOH jump: determination of deprotonation rates of water by 6-methoxyquinoline and acridine. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100281a061] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Intramolecular donor-acceptor systems. 7. Solvent dielectric relaxation effects on the photophysics of 6-(phenylamino)-N,N-dimethyl-2-naphthalenesulfonamides. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100237a010] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Photodissociation of haloaromatics: detection, kinetics, and mechanism of arylmethyl radical formation. J Am Chem Soc 2002. [DOI: 10.1021/ja00319a009] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Pressure dependence of excited-state intramolecular electron-transfer dynamics in polar solvents. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100330a026] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Studies of surface recombination velocity at copper/cadmium sulfide (1120) interfaces. ACTA ACUST UNITED AC 2002. [DOI: 10.1021/j100380a055] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Experimental evidence for a kinetic transition in reversible reactions. PHYSICAL REVIEW LETTERS 2001; 86:3427-3430. [PMID: 11327987 DOI: 10.1103/physrevlett.86.3427] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/29/2000] [Indexed: 05/23/2023]
Abstract
We provide a first experimental verification of a theoretical prediction of a kinetic transition in a reversible binding reaction, AB right harpoon over left harpoon A+B, driven by the difference in effective lifetimes of the bound and the unbound states. We consider the kinetics of excited-state proton transfer to solvent from a photoacid whose conjugate anionic base possesses an extremely short unbound anion lifetime. Its solvent variation relative to the overall dissociation rate coefficient induces a transition in the kinetics, from power law to exponential.
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Abstract
Pyranine (8-hydroxy pyrene-1,3,6-trisulfonate) is a commonly used photoacid that discharges a proton when excited to its first electronic singlet state. Follow-up of its dissociation kinetics reveals the physicochemical properties of its most immediate environment. At vanishing ionic strength the dye adsorbs to the Escherichia coli lactose permease with stoichiometry of 1:1 and an association constant of 2.5 x 10(5) M(-1). The reversal of the binding at high ionic strength and the lower pK value of the bound dye imply that positive charge(s) stabilize the dye in its site. The fluorescence decay curve of the bound dye was measured by time-correlated single photon counting and the measured transient was subjected to kinetic analysis based on the geminate recombination model. The analysis indicated that the binding domain is a cleft (between 9 and 17 A deep) characterized by low activity of water (a((water)) = 0.71), reduced diffusivity of protons, and enhanced electrostatic potential. The binding of pyranine and a substrate are not mutually exclusive; however, when the substrate is added, the dye-binding environment is better solvated. These properties, if attributed to the substrate-conducting pathway, may explain some of the forces operating on the substrate in the cavity. The reduced activities of the water strips the substrate from some of its solvation water molecules and replace them by direct interaction with the protein. In parallel, the lower dielectric constant enhances the binding of the proton to the protein, thus keeping a tight seal that prevents protons from diffusing.
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Solvation Statics and Dynamics in Electrolyte Solutions. The Ion−Solvent Exchange Model. J Phys Chem A 2000. [DOI: 10.1021/jp000917k] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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