Improving the Accuracy and Reliability of Remote System-Calibration-Free Eye-Gaze Tracking

Remote eye-gaze tracking provides a means for nonintrusive tracking of the point-of-gaze (POG) of a user. For application as a user interface for the disabled, a remote system that is noncontact, reliable, and permits head motion is very desirable. The system-calibration-free pupil-corneal reflection (P-CR) vector technique for POG estimation is a popular method due to its simplicity, however, accuracy has been shown to be degraded with head displacement. Model-based POG-estimation methods were developed, which improve system accuracy during head displacement, however, these methods require complex system calibration in addition to user calibration. In this paper, the use of multiple corneal reflections and point-pattern matching allows for a scaling correction of the P-CR vector for head displacements as well as an improvement in system robustness to corneal reflection distortion, leading to improved POG-estimation accuracy. To demonstrate the improvement in performance, the enhanced multiple corneal reflection P-CR method is compared to the monocular and binocular accuracy of the traditional single corneal reflection P-CR method, and a model-based method of POG estimation for various head displacements.     

CaII Binding Regulates and Dominates the Reactivity of a Transition‐Metal‐Ion‐Dependent Diesterase from Mycobacterium tuberculosis

The diesterase Rv0805 from Mycobacterium tuberculosis is a dinuclear metallohydrolase that plays an important role in signal transduction by controlling the intracellular levels of cyclic nucleotides. As Rv0805 is essential for mycobacterial growth it is a promising new target for the development of chemotherapeutics to treat tuberculosis. The in vivo metal‐ion composition of Rv0805 is subject to debate. Here, we demonstrate that the active site accommodates two divalent transition metal ions with binding affinities ranging from approximately 50 nm for Mn^II to about 600 nm for Zn^II. In contrast, the enzyme GpdQ from Enterobacter aerogenes, despite having a coordination sphere identical to that of Rv0805, binds only one metal ion in the absence of substrate, thus demonstrating the significance of the outer sphere to modulate metal‐ion binding and enzymatic reactivity. Ca^II also binds tightly to Rv0805 (K_d≈40 nm ), but kinetic, calorimetric, and spectroscopic data indicate that two Ca^II ions bind at a site different from the dinuclear transition‐metal‐ion binding site. Ca^II acts as an activator of the enzymatic activity but is able to promote the hydrolysis of substrates even in the absence of transition‐metal ions, thus providing an effective strategy for the regulation of the enzymatic activity.     

Efficient kinetic bioresolution of 2-nitrocyclohexanol

The kinetic bioresolution of 2-nitrocyclohexanol 1 was investigated by screening a range of hydrolases both for enantioselective transesterification and for enantioselective hydrolysis of the corresponding acetate. By appropriate choice of biocatalyst and conditions, both enantiomers of cis and trans 2-nitrocyclohexanol 1 can be accessed in enantiopure form.