Search

We have studied the effect of monomerization of the purple membrane lattice, as well as removal of 75% of the lipids, on the binding properties of Eu3+ ions. We found that delipidation and monomerization do not cause the cations to lose their binding ability to the protein. This suggests that the three most strongly bound Eu3+ cations do not bind to the lipids, but directly bind to the protein. Furthermore, we found that delipidation actually causes a slight increase in the binding affinity. This is likely a result of reduced aggregation of europium-regenerated bacteriorhodopsin (bR) upon lipid removal causing more exposure of the binding sites to the Eu3+ cations. These results, taken with those from our previous publication [Heyes and El-Sayed, Biophys. J. 85 (2003) 426–434], might suggest that the cations remain bound upon delipidation of bR, but have no effect on the function. This is discussed with respect to the role of cations in the function of native bR. [Copyright &y& Elsevier]

Blind pedestrians lack preview of their environment and as a consequence they frequently adopt a slow walking speed. Electronic mobility aids have been designed to increase preview, and thus thinking time, over and above that provided by a long cane, but their ranges have been chosen on somewhat arbitrary grounds. Previous work on the effects of varying preview upon mobility have used artificial indoor environments. In addition, they have used either sight or an aid with a complicated display, the Swedish Laser Cane, as the medium through which to present the preview. The present experiment provided subjects with varying amounts of preview via an electronic mobility aid, the Sonic Pathfinder, as they walked a simple outdoor route. Their walking speed was recorded and found to increase significantly with increased preview. The range of the Sonic Pathfinder has now been increased on the strength of this experiment. [ABSTRACT FROM PUBLISHER]

All pedestrians have a walking speed which they prefer. This appears to be the speed which, for them, is the most physically efficient. Blind pedestrians, if allowed to set the pace when accompanied by a sighted guide, will prefer to walk at a speed which is close to that of sighted pedestrians. However, when walking independently they adopt a pace which is slower than their preferred walking speed. By converting adopted walking speed into a proportion of preferred walking speed we are able to show that subject data may be pooled and comparisons made which had hitherto been impossible. Furthermore, statements may be made about the physiological efficiency of a performance. For example, efficiency varies with route difficulty, increases with increased preview, and only users of guide dogs reach their optimum efficiency. [ABSTRACT FROM PUBLISHER]

A series of studies assessed the extent to which different versions for a £1 coin might be confused with existing coins. The first experiment demonstrated that a milled coin of 22 mm diameter and 2*8 mm thickness would be confused with the 5p by touch. The experiment was repeated with a coin 315 mm thick and the error-rate was greatly reduced. A third experiment compared the two different thicknesses directly, and also included a 3-15 mm coin with a different edge (interrupted milling) for comparison. Both the thicker coins produced similar performance, which was again better than that achieved with the 2-8 mm version. In experiment 4, three different thicknesses of the £1 coin were presented for identification to a sample of blind and partially-sighted subjects. The thinnest version (2-7 mm) was frequently confused with the 5p, but the thickest version (3-1 mm) was rarely confused. Finally the thickest version was included in a study in which sighted subjects sorted coins in dim light. Under these conditions there was again some confusion between the £1 and the 5p. [ABSTRACT FROM PUBLISHER]

Although blind pedestrians have a significantly higher heart rate when walking independently than when walking guided, no relationship between instantaneous heart rate and specific stressful environmental events has yet been demonstrated. However, such a relationship has been observed in a number of sighted tasks such as car driving. This study has compared the heart rates of four subjects performing both blind mobility and driving tasks and has shown that individuals who exhibit local stress effects during car driving do not show comparable efforts whilst walking independently under blindfold. [ABSTRACT FROM PUBLISHER]

Protein targeting is critical in all living organisms and involves a signal recognition particle (SRP), an SRP receptor, and a translocase. In co-translational targeting, interactions among these proteins are mediated by the ribosome. In chloroplasts, the light-harvesting chlorophyll-binding protein (LHCP) in the thylakoid membrane is targeted post-translationally without a ribosome. A multidomain chloroplast-specific subunit of the SRP, cpSRP43, is proposed to take on the role of coordinating the sequence of targeting events. Here, we demonstrate that cpSRP43 exhibits significant interdomain dynamics that are reduced upon binding its SRP binding partner, cpSRP54. We showed that the affinity of cpSRP43 for the binding motif of LHCP (L18) increases when cpSRP43 is complexed to the binding motif of cpSRP54 (cpSRP54pep). These results support the conclusion that substrate binding to the chloroplast SRP is modulated by protein structural dynamics in which a major role of cpSRP54 is to improve substrate binding efficiency to the cpSRP. [ABSTRACT FROM AUTHOR]

Purpose: To develop a new test of activities of daily living (ADLs) appropriate for the low-vision population: the Melbourne Low-Vision ADL Index (MLVAI)., Methods: The MLVAI was designed as a desk-based clinical assessment, comprising 18 observed items on complex ADLs in part (a) and 9 questions on broad self-care ADLs in part (b). Each item was rated on a five-level descriptive scale from 0 to 4, based on independence, speed, and accuracy of performance. It was designed to be administered under standardized conditions with regard to the instructions, illumination, and working distances. The validity and reliability of the new MLVAI was determined for 122 subjects who were representative of the general low-vision population, in a cross-sectional study., Results: Two items were found to be redundant and were eliminated from the test. Thus, the final test comprised 25 items, with 100 being the highest possible score. Cronbach's alpha indicated an internal reliability of 0.96, and an intraclass correlation coefficient indicated an overall reliability of 0.95. The SE of measurement was 4.5. According to Spearman's correlation coefficient, the test-retest reliability was 0.94 (P < 0.001), and the interpractitioner reliability for five different pairs of practitioners was 0.90 or higher (P < 0.001). With regard to validity, there was a moderately high correlation with vision impairment (r = -0.68, P < 0.001). Using Rasch analysis, content validity was also demonstrated by good separation indexes (4.70 and 9.88) and high reliability scores (0.96 and 0.99) for the person and items parameters, respectively. Separate calculation of indexes and reliability scores for parts (a) and (b) indicated high content validity and reliability of each part. However, the separation indexes and reliability scores were higher for part (a) than for part (b). The correlation coefficient for part (a) and part (b) was 0.68., Conclusions: The MLVAI is a highly valid and reliable standardized test of ADL performance for the general low-vision population. It may be used to assess patients with low vision and has the potential to be used as a measure of low-vision rehabilitation outcomes.