Engineering highly thermostable Cas12b via de novo structural analyses for one-pot detection of nucleic acids

CRISPR-Cas-based diagnostics have the potential to elevate nucleic acid detection. CRISPR-Cas systems can be combined with a pre-amplification step in a one-pot reaction to simplify the workflow and reduce carryover contamination. Here, we report an engineered Cas12b with improved thermostability that falls within the optimal temperature range (60°C-65°C) of reverse transcription-loop-mediated isothermal amplification (RT-LAMP). Using de novo structural analyses, we introduce mutations to wild-type BrCas12b to tighten its hydrophobic cores, thereby enhancing thermostability. The one-pot detection assay utilizing the engineered BrCas12b, called SPLENDID (single-pot LAMP-mediated engineered BrCas12b for nucleic acid detection of infectious diseases), exhibits robust trans-cleavage activity up to 67°C in a one-pot setting. We validate SPLENDID clinically in 80 serum samples for hepatitis C virus (HCV) and 66 saliva samples for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) with high specificity and accuracy. We obtain results in as little as 20 min, and with the extraction process, the entire assay can be performed within an hour.

Desert wanderings: pathways for whole, broken and shattered psyches

This paper challenges an implicit assumption of analytical psychology that centred, mandalic images express psychical wholeness in an optimal fashion across cultures and eras. I suggest that liminal, bardo-like eras, such as our 'post-modern' one, constellate complex, antithetical and ec-centric images, which are process-oriented and which encompass wholeness and fragmentation, conjunction and disjunction, thus holding and expressing actual individual and collective experience. In our era, we inhabit unfolding states of wholeness, brokenness and fragmentation. Images of wholeness, emerging spontaneously from the unconscious, may reflect part or all of these contradictory realities. Examples of such antithetical Self-images are developed from the ancient midrashic traditions of the rabbis; from Jung's contemporary exposition of Pauli's 'world-clock' dream; from Kepler's discovery, at the dawn of modernity, that the planets circled the sun in ellipses rather than circles; and from a clinical illustration.

Subjective evaluation of four low-complexity audio coding schemes

In this study the subjective performance of four low-complexity audio data compression methods are compared, operating at nominal bit rates of 2, 3, 4, and 5 bits per sample, applied to four 20-kHz bandwidth, 16-bits per sample digitized musical signals. The simple compression schemes compared were elementary differential pulse-code modulation (DPCM), noise feedback coding DPCM (NFC-DPCM), adaptive quantizer DPCM (DPCM-AQB), and a recently proposed method known as recursively indexed quantizer DPCM (RIQ-DPCM). Pairs consisting of a reconstructed signal and a reference signal were presented in a two-interval preference experiment. The reference signals were processed for specified levels of modulated noise reference unit (MNRU) in order to estimate the equality threshold rating (ETR) of the reconstructed audio stimuli. The subjective MNRU values were found to increase by 2-5 dB for each increment in bits per sample. The DPCM-AQB scores were found to be 8-10 dB higher than for DPCM and NFC-DPCM. RIQ-DPCM was rated highest, exceeding the DPCM-AQB results by 2-5 dB in all tests. Objective measurements of segmental signal-to-noise ratio (SNRSEG) for the reconstructed signals predicted a performance level 2-5 dB lower than was actually found in the subjective results, particularly for SNRSEG values below 25 dB.

Preliminary evaluation of a new curriculum--incorporation of problem based learning (PBL) into the traditional format

An account of the establishment of a Problem Based Learning (PBL) curriculum at the Eric Williams Medical Science Complex Republic of Trinidad and Tobago provides the forum for a critical analysis of this process and for dialogue with current relevant literature on similar attempts elsewhere. Initial resistance to change and the assessment of the new system is discussed in the light of the fact that this is the first Caribbean territory to adopt Problem Based Learning as the major instrument to be employed in tertiary level medical education. The analysis uncovers a model of practitioner/researcher which provides a useful conceptual and operational framework for the articulation of the role of those engaged in effecting and studying the management of change.