DNA is an attractive candidate for integration into nanoelectronics as a biological nanowire due to its linear geometry, definable base sequence, easy, inexpensive and non-toxic replication and self-assembling properties. Recently we discovered that by intercalating Ag + in polycytosine-mismatch oligonucleotides, the resulting C-Ag + -C duplexes are able to conduct charge efficiently. To map the functionality and biostability of this system, we built and characterized internally-functionalized DNA nanowires through non-canonical, Ag + -mediated base pairing in duplexes containing cytosine-cytosine mismatches. We assessed the thermal and chemical stability of ion-coordinated duplexes in aqueous solutions and conclude that the C-Ag + -C bond forms DNA duplexes with replicable geometry, predictable thermodynamics, and tunable length. We demonstrated continuous ion chain formation in oligonucleotides of 11–50 nucleotides (nt), and enzyme ligation of mixed strands up to six times that length. This construction is feasible without detectable silver nanocluster contaminants. Functional gene parts for the synthesis of DNA- and RNA-based, C-Ag + -C duplexes in a cell-free system have been constructed in an Escherichia coli expression plasmid and added to the open-source BioBrick Registry, paving the way to realizing the promise of inexpensive industrial production. With appropriate design constraints, this conductive variant of DNA demonstrates promise for use in synthetic biological constructs as a dynamic nucleic acid component and contributes molecular electronic functionality to DNA that is not already found in nature. We propose a viable route to fabricating stable DNA nanowires in cell-free and synthetic biological systems for the production of self-assembling nanoelectronic architectures.

Introduction Sensory feedback is largely unavailable for persons with upper-limb amputation with conventional prostheses. The current study created a portable vibratory haptic feedback system integrated into the prosthesis to test its usefulness in gripping objects during daily life. Materials and Methods Development involved optimizing a mapping algorithm between the force sensor and the feedback tactor vibration, developing a custom process for mounting a wireless force sensor onto the prosthetic thumb with reliable output, and developing an instrumented object for testing grip force accuracy. Clinical testing involved optimizing tactor placement, measuring grip force accuracy, measuring the ability to perform daily gripping tasks, and surveying prosthetic users' opinion of the system after using the vibratory haptic device at home. A total of six individuals with unilateral transradial amputation participated in this study. Results The results demonstrated optimal tactor placement more proximal versus distal on the forearm. Accuracy with haptic versus no haptic feedback demonstrated that haptic feedback improved the grip force accuracy by 129% (adjusted P = 0.041) for light grip force target (2 lb or 0.9 kg) in the nonportable system and 21% (adjusted P = 0.051) for medium grip force target (10 lb or 4.5 kg) in the portable system. Haptic feedback did not statistically improve grip accuracy at strong grip forces (20 lb or 9.1 kg). Haptic feedback improved the gripping technique during the Assessment of Capacity for Myoelectric Control (ACMC) by 1.22 points, although this was not statistically significant (P = 0.27, n = 4). The participants provided specific positive examples of how the vibratory haptic system was useful at home. The overall usability score was 3.6 where 4 indicated excellent and 0 indicated poor. Conclusions This kind of system has potential to improve the lives of upper-limb prosthetic users.

Kim and Opfer (2017) report data that demonstrate children produce a negatively accelerating (e.g., logarithmic) response pattern in the unbounded number-line task. This pattern of results is the opposite of those generally reported for the unbounded number-line task (e.g., Cohen & Blanc-Goldhammer, 2011;Cohen & Sarnecka, 2014). We believe Kim and Opfer's (2017) experimental procedure inadvertently biased participants' data in the unbounded task. Here, we (a) outline the factors that induce experimental bias in computerized number-line tasks, (b) identify the likely source of experimental bias in Kim and Opfer (2017) that led to the negatively accelerating pattern of data, (c) introduce a new number-line variation (the universal number-line task), and (d) introduce a publicly available, open source number-line task that provides researchers with a simple, robust, and correct method for collecting data on the unbounded, bounded, and universal number-line tasks. We conclude that Kim and Opfer's (2017) implementation of the unbounded number-line is biased, and therefore cannot provide meaningful support for the log-to-linear shift hypothesis.

No abstract