Reading amino acids by nanopore Nanopore technology enables sensing of minute chemical changes at the single-molecule level by detecting differences in an ion current as molecules are drawn through a membrane-embedded pore. The sensitivity is sufficient to discriminate between nucleotide bases in nanopore sequencing, and other applications of this technology are promising. Brinkerhoff et al . developed a nanopore-based, single-molecule approach in which a protein was sequentially scanned in single-amino-acid steps through the narrow construction of a nanopore, and ion currents were monitored to resolve differences in the amino acid sequence along the peptide backbone (see the Perspective by Bošković and Keyser). The peptide reader was capable of reliably detecting single-amino-acid substitutions within individual peptides. An individual protein could be re-read many times, yielding very high read accuracy in variant identification. These proof-of-concept nanopore experiments constitute a promising basis for the development of a single-molecule protein sequencer. —DJ

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The ability of Mycobacterium tuberculosis (M. tb) to survive and persist in the host for decades in an asymptomatic state is an important aspect of tuberculosis pathogenesis. Although adaptation to hypoxia is thought to play a prominent role underlying M. tb persistence, how the bacteria achieve this goal is largely unknown. Rv0081, a member of the DosR regulon, is induced at the early stage of hypoxia while Rv3334 is one of the enduring hypoxic response genes. In this study, we uncovered genetic interactions between these two transcription factors. RNA-seq analysis of ΔRv0081 and ΔRv3334 revealed that the gene expression profiles of these two mutants were highly similar. We also found that under hypoxia, Rv0081 positively regulated the expression of Rv3334 while Rv3334 repressed transcription of Rv0081. In addition, we demonstrated that Rv0081 formed dimer and bound to the promoter region of Rv3334. Taken together, these data suggest that Rv0081 and Rv3334 work in the same regulatory pathway and that Rv3334 functions immediately downstream of Rv0081. We also found that Rv3334 is a bona fide regulator of the enduring hypoxic response genes. Our study has uncovered a regulatory pathway that connects the early and the enduring hypoxic response, revealing a transcriptional cascade that coordinates the temporal response of M. tb to hypoxia.

Increased‐risk donor (IRD) organs make up a significant proportion of the deceased organ donor pool but may be declined by patients on the waiting list for various reasons. We conducted a survey of patients awaiting a liver transplant to determine the factors leading to the acceptance of an IRD organ as well as what strategies could increase the rate of acceptance. Adult liver transplant candidates who were outpatients completed a survey of 51 questions on a 5‐point Likert scale with categories related to demographics, knowledge of IRDs, and likelihood of acceptance. A total of 150 transplant candidates completed the survey (age 19‐80 years). Male patients constituted 67.3%. Many patients (58.7%) had postsecondary education. Only 23.3% of patients had a potential living donor, and 58/144 (40.3%) were not optimistic about receiving an organ in the next 3 months. The overall IRD organ acceptance rate was 41.1%, whereas 26.2% said they would decline an IRD organ. Women were more likely to accept an IRD organ (54.3% versus 34.7%; P = 0.02). Those who had a college education or higher tended to have lower IRD organ acceptability (28.3% versus 47.4%; P = 0.07). Acceptability also increased as the specified transmission risk of human immunodeficiency virus or hepatitis C virus decreased (P < 0.001). Patients were also more likely to accept an IRD organ if they were educated on the benefits of IRD organs (eg, knowledge that an IRD organ was of better quality increased overall acceptance from 41.1% to 63.3%; P < 0.001). Our survey provides insight into liver transplant candidates who would benefit from greater education on IRD organs. Strategies targeting specific educational points are likely to increase acceptability.

DNA is a promising next-generation data storage medium, but challenges remain with synthesis costs and recording latency. Here, we describe a prototype of a DNA data storage system that uses an extended molecular alphabet combining natural and chemically modified nucleotides. Our results show that MspA nanopores can discriminate different combinations and ordered sequences of natural and chemically modified nucleotides in custom-designed oligomers. We further demonstrate single-molecule sequencing of the extended alphabet using a neural network architecture that classifies raw current signals generated by Oxford Nanopore sequencers with an average accuracy exceeding 60% (39× larger than random guessing). Molecular dynamics simulations show that the majority of modified nucleotides lead to only minor perturbations of the DNA double helix. Overall, the extended molecular alphabet may potentially offer a nearly 2-fold increase in storage density and potentially the same order of reduction in the recording latency, thereby enabling new implementations of molecular recorders.

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Postgate annealing (PGA) in N 2 /O 2 atmosphere at 300°C for various annealing time is performed on enhancement mode AlGaN/GaN MOSFET fabricated using a self-terminating gate recess etching technique. After 45-min annealing, the device OFF-state leakage current decreases by more than two orders of magnitude and thus a low OFF-state leakage current of ∼10 −13 A/mm is obtained at room temperature, resulting in an excellent ON/OFF current ratio of ∼10 12 . At 250°C, the device still exhibits a low OFF-state leakage current of ∼10 −9 A/mm and high ON/OFF current ratio of ∼10 8 . Meanwhile, a strong correlation between the OFF-state leakage current and mesa isolation current is observed as we change the annealing time: 1) the lower the mesa isolation current and 2) the lower the OFFstate leakage current and thus the higher the ON/OFF current ratio. It is the suppression of the mesa isolation current owing to the passivation of atomic layer deposition Al 2 O 3 that leads to the improvement of the OFF-state leakage current and ON/OFF current ratio after PGA. Besides, the device shows no obvious change in terms of its threshold voltage and maximum drain current after PGA.Index Terms-Post-gate annealing (PGA), GaN, enhancement mode, MOSFET, ON/OFF current ratio, mesa isolation current.