Enhanced Yield and Gentle Purification of HIV for Cryo-Electron Tomography Analysis of Virion Maturation.

HIV is a lentivirus characterized by the formation of its mature core. Visualization and structural examination of HIV requires purification of virions to high concentrations. The yield and integrity of these virions are crucial for ensuring a uniform representation of all viral particles in subsequent analyses.

Competitive assembly resolves the stoichiometry of essential proteins in infectious HIV-1 virions.

Unlabelled: During assembly on the plasma membrane, HIV-1 virions incorporate Gag-Pol as well as gp120/gp41 trimers. The Pol region consists of protease, reverse transcriptase and integrase precursors which are essential enzymes required for maturation, reverse transcription, and integration of the viral genome in the next host. gp120/gp41 trimers catalyze the fusion of the virion with its next host.

On the optimal measurement of conversion gain in the presence of dark noise.

Working from a model of Gaussian pixel noise, we present and unify over 25 years of developments in the statistical analysis of the photon transfer conversion gain measurement. We then study a two-sample estimator of the conversion gain that accounts for the general case of non-negligible dark noise. The moments of this estimator are ill-defined (their integral representations diverge), and so we propose a method for assigning pseudomoments, which are shown to agree with actual sample moments under mild conditions.

3D noise photon transfer curve.

A photon transfer curve (PTC) is used to determine fundamental detector noise parameters such as read noise, conversion gain, and fixed pattern noise. Here, the method for determining a PTC is expanded to include 3D noise parameters. 3D noise PTC provides more insight into detector noise and is treated as the next logical step to classical PTC.

Gag-Gag Interactions Are Insufficient to Fully Stabilize and Order the Immature HIV Gag Lattice.

Immature HIV virions harbor a lattice of Gag molecules with significant ordering in CA-NTD, CA-CTD and SP1 regions. This ordering plays a major role during HIV maturation. To test the condition in which the Gag lattice forms in vivo, we assembled virus like particles (VLPs) by expressing only HIV Gag in mammalian cells.

Minimal system for assembly of SARS-CoV-2 virus like particles.

SARS-CoV-2 virus is the causative agent of COVID-19. Here we demonstrate that non-infectious SARS-CoV-2 virus like particles (VLPs) can be assembled by co-expressing the viral proteins S, M and E in mammalian cells. The assembled SARS-CoV-2 VLPs possess S protein spikes on particle exterior, making them ideal for vaccine development.

Structural stability of SARS-CoV-2 virus like particles degrades with temperature.

SARS-CoV-2 is a novel coronavirus which has caused the COVID-19 pandemic. Other known coronaviruses show a strong pattern of seasonality, with the infection cases in humans being more prominent in winter. Although several plausible origins of such seasonal variability have been proposed, its mechanism is unclear.

Structural stability of SARS-CoV-2 degrades with temperature.

Unlabelled: SARS-CoV-2 is a novel coronavirus which has caused the COVID-19 pandemic. Other known coronaviruses show a strong pattern of seasonality, with the infection cases in humans being more prominent in winter. Although several plausible origins of such seasonal variability have been proposed, its mechanism is unclear.

Experimentally measuring a detectability index of a computational imaging system.

Computational imaging (CI) systems are an enabling technology for multifunctional cameras capable of performing a wide variety of imaging tasks. However, given the complexity of CI systems, it is often difficult to characterize their performance. In this research, a novel measurement technique is proposed and tested to evaluate the performance of complex non-shift invariant linear CI systems performing a detection task at the system level.

Standardized target-specific detectivity metric for computational imaging systems.

Multifunctional cameras capable of performing a wide variety of nearly simultaneous imaging tasks are expected to play a major role in the near future. Computational imaging (CI) systems will serve as one of the main enabling technologies for multifunctional cameras, especially due to the abundance of low-cost, high-speed computational processing available today. An important aspect of these systems is to be able to quantify their performance with respect to specific imaging tasks.

Dandy-Walker malformation in two calves.

Two calves with unusual malformations of the skull and brain are described. Both calves showed doming of the posterior skull due to enlargement of the posterior fossa and cyst-like dilatation of the fourth ventricle. The cystic dilatation of the fourth ventricle formed a meningocoele in one calf.