Three dimensional (3‐D) fluorescence microscopes, including conventional instruments with digital deblurring, confocal systems and two‐photon excitation, all exhibit monochromatic and chromatic aberrations. A simple Gaussian model of the aberrated point spread function and optical field for each instrument illustrates spatial distortions and blurring and some unique attenuation effects in confocal and two‐photon microscopy. These properties depend on the manner in which illumination and detection combine to give the overall microscope performance and highlight the importance of both optics and sample aberrations; the specimen must be considered as an optical component of the integrated imaging system. Axial focus distortion, from refractive index boundaries at the sample, can be accurately modelled by a geometric ray tracing programme, considering weighted components across the entire objective lens working NA. The modal z‐focus error, rather than the average of all weighted rays, agrees closely with empirical measurements of axial focus position from test samples. This agreement is particularly close for confocal measurements when NA4 weighting is used in the model calculations, but the situation is more complex for samples with non‐planar refractive boundaries. Calibration of axial attenuation in a botanical sample, arising from the combination of optical sectioning with specimen‐induced spatial distortions and blurring, is possible using an in situ fluorescence sea within a permeabilized preparation. Parametric descriptions of attenuation can be obtained through the guard cell complex of Commelina communis leaf epidermis. Improved images of the 3‐D morphology of stomatal guard cells are then obtained by digital correction of attenuation and spatial distortion. Calibrations can be routinely used to correct experimental data by integration with a structured image file format.

The virus‐like particles (VLPs) of the yeast retrotransposon Ty are genetically, structurally and functionally analogous to retroviral nucleocapsids or cores. Like retroviral cores Ty‐VLPs package and possibly promote the enzyme activities for reverse transcription and integration, as well as encapsulating the RNA that is the intermediate in retrotransposition. Here we show that Ty‐VLPs assemble into symmetrical structures across a broad distribution of particle sizes. This spread of sizes violates the principle of quasi‐equivalent packing. In addition, RNase accessibility experiments suggest that these particles form an open structure that does not protect the encapsulated RNA. These features distinguish Ty‐VLPs from typical spherical viral capsids in both structure and function.

BRCA1 interacts with ERM proteins at leading edges and focal adhesion sites and modulates motility via its ubiquitin ligase activity.

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Retinal and intra-retinal layer thicknesses are routinely generated from optical coherence tomography (OCT) images, but on-board software capabilities and image scaling assumptions are not consistent across devices. This study evaluates the device-independent Iowa Reference Algorithms (Iowa Institute for Biomedical Imaging) for automated intra-retinal layer segmentation and image scaling for three OCT systems. Healthy participants (n = 25) underwent macular volume scans using a Cirrus HD-OCT (Zeiss), 3D-OCT 1000 (Topcon), and a non-commercial long-wavelength (1040nm) OCT on two occasions. Mean thickness of 10 intra-retinal layers was measured in three ETDRS subfields (fovea, inner ring and outer ring) using the Iowa Reference Algorithms. Where available, total retinal thicknesses were measured using on-board software. Measured axial eye length (AEL)-dependent scaling was used throughout, with a comparison made to the system-specific fixed-AEL scaling. Inter-session repeatability and agreement between OCT systems and segmentation methods was assessed. Inter-session coefficient of repeatability (CoR) for the foveal subfield total retinal thickness was 3.43μm, 4.76μm, and 5.98μm for the Zeiss, Topcon, and long-wavelength images respectively. For the commercial software, CoR was 4.63μm (Zeiss) and 7.63μm (Topcon). The Iowa Reference Algorithms demonstrated higher repeatability than the on-board software and, in addition, reliably segmented all 10 intra-retinal layers. With fixed-AEL scaling, the algorithm produced significantly different thickness values for the three OCT devices (P<0.05), with these discrepancies generally characterized by an overall offset (bias) and correlations with axial eye length for the foveal subfield and outer ring (P<0.05). This correlation was reduced to an insignificant level in all cases when AEL-dependent scaling was used. Overall, the Iowa Reference Algorithms are viable for clinical and research use in healthy eyes imaged with these devices, however ocular biometry is required for accurate quantification of OCT images.