Shapes of Discoid Intracellular Compartments with Small Relative Volumes

A prominent feature of many intracellular compartments is a large membrane surface area relative to their luminal volume, i.e., the small relative volume. In this study we present a theoretical analysis of discoid membrane compartments with a small relative volume and then compare the theoretical results to quantitative morphological assessment of fusiform vesicles in urinary bladder umbrella cells. Specifically, we employ three established extensions of the standard approach to lipid membrane shape calculation and determine the shapes that could be expected according to three scenarios of membrane shaping: membrane adhesion in the central discoid part, curvature driven lateral segregation of membrane constituents, and existence of stiffer membrane regions, e.g., support by protein scaffolds. The main characteristics of each scenario are analyzed. The results indicate that even though all three scenarios can lead to similar shapes, there are values of model parameters that yield qualitatively distinctive shapes. Consequently, a distinctive shape of an intracellular compartment may reveal its membrane shaping mechanism and the membrane structure. The observed shapes of fusiform vesicles fall into two qualitatively different classes, yet they are all consistent with the theoretical results and the current understanding of their structure and function

An oomycete NLP cytolysin forms transient small pores in lipid membranes

Microbial plant pathogens secrete a range of effector proteins that damage host plants and consequently constrain global food production. Necrosis and ethylene-inducing peptide 1-like proteins (NLPs) are produced by numerous phytopathogenic microbes that cause important crop diseases. Many NLPs are cytolytic, causing cell death and tissue necrosis by disrupting the plant plasma membrane. Here, we reveal the unique molecular mechanism underlying the membrane damage induced by the cytotoxic model NLP. This membrane disruption is a multistep process that includes electrostatic-driven, plant-specific lipid recognition, shallow membrane binding, protein aggregation, and transient pore formation. The NLP-induced damage is not caused by membrane reorganization or large-scale defects but by small membrane ruptures. This distinct mechanism of lipid membrane disruption is highly adapted to effectively damage plant cells.Peer reviewe

Programable Stroboscopic Illumination for Microscopy

A low-cost stroboscopic illumination for microscop

Software

Software written by David Lajevec & Jure Dergan

3D-printed housing

TLS files made by Rok Štan

Membrane bending by protein crowding is affected by protein lateral confinement.

International audienceCrowding of asymmetrically-distributed membrane proteins has been recently recognized as an important factor in remodeling of biological membranes, for example during transport vesicle formation. In this paper, we theoretically analyze the effect of protein crowding on membrane bending and examine its dependence on protein size, shape, transmembrane asymmetry and lateral confinement. We consider three scenarios of protein lateral organization, which are highly relevant for cellular membranes in general: freely diffusing membrane proteins without lateral confinement, the presence of a diffusion barrier and interactions with a vesicular coat. We show that protein crowding affects vesicle formation even if the proteins are distributed symmetrically across the membrane and that this effect depends significantly on lateral confinement. The largest crowding effect is predicted for the proteins that are confined to the forming vesicle by a diffusion barrier. We calculate the bending properties of a crowded membrane and find that its spontaneous curvature depends primarily on the degree of transmembrane asymmetry, and its effective bending modulus on the type of lateral confinement. Using the example of COPII vesicle formation from the endoplasmic reticulum, we analyze the energetic cost of vesicle formation. The results provide a novel insight into the effects of lateral and transmembrane organization of membrane proteins, and can guide data interpretation and future experimental approaches

Priredba freiburškega enozložnega besednega preizkusa za slovenščino

Speech audiometry is one of the standard methods used to diagnose the type of hearing loss and to assess the communication function of the patient by determining the level of the patient’s ability to understand and repeat words presented to him or her in a hearing test. For this purpose, the Slovenian adaptation of the German tests developed by Hahlbrock (1953, 1960) – the Freiburg Monosyllabic Word Test and the Freiburg Number Test – are used in Slovenia (adapted in 1968 by Pompe). In this paper we focus on the Freiburg Monosyllabic Word Test for Slovenian, which has been criticized by patients as well as in the literature for the unequal difficulty and frequency of the words, with many of these being extremely rare or even obsolete. As part of the patient’s communication function is retrieving the meaning of individual words by guessing, the less frequent and consequently less familiar words do not contribute to reliable testing results. We therefore adapt the test by identifying and removing such words and supplement them with phonetically similar words to preserve the phonetic balance of the list. The words used for replacement are extracted from the written corpus of Slovenian Gigafida and the spoken corpus of Slovenian GOS, while the optimal combinations of words are established by using computational algorithms.Govorna avdiometrija je eden od standardnih diagnostičnih pripomočkov pri ugotavljanju različnih tipov slušnega primanjkljaja ter pri preverjanju sporazumevalne funkcije pri pacientu, kjer s pomočjo testov slušne zaznave preverjamo, kakšna je pacientova zmožnost razumeti in ponoviti besede iz testa. V Sloveniji je v rabi Freiburški govorni preizkus (enozložni besedni in številčni preizkus), ki ga je razvil Hahlbrock (Hahlbrock 1953, 1960), za slovenske govorce pa leta 1968 priredil Pompe. V članku se osredotočimo na enozložni besedni preizkus, za katerega je bilo ugotovljeno veliko pomanjkljivosti predvsem z vidika pogostosti besed, saj test vsebuje kar precejšnje število izjemno redkih ali celo zastarelih besed. Ker je del sporazumevalne funkcije pri govorcu tudi zmožnost ugibanja slišane besede, je pri velikem številu govorcu neznanih besed pod vprašajem veljavnost izmerjenega rezultata, saj neznane besede govorec težje ugane. Test prenovimo tako, da najprej identificiramo manj pogoste in zastarele besede ter jih zamenjamo s fonetično podobnimi besedami, da obdržimo fonetično uravnoteženost testa. Nadomestne besede poiščemo z uporabo pisnega korpusa slovenščine Gigafida ter korpusa govorjene slovenščine GOS. Najbolj ustrezno kombinacijo nadomestnih besed, ki ohranja fonetično uravnoteženost testa, določimo z uporabo računskih algoritmov

Membrane bending: the power of protein imbalance.

International audienceMany cellular processes require membrane deformation, which is driven by specialized protein machinery and can often be recapitulated using pure lipid bilayers. However, biological membranes contain a large amount of embedded proteins. Recent research suggests that membrane-bound proteins with asymmetric distribution of mass across the bilayer can influence membrane bending in a nonspecific manner due to molecular crowding. This mechanism is physical in nature and arises from collisions between such 'mushroom-shaped' proteins. It can either facilitate or impede the action of protein coats, for example COPII, during vesicle budding. We describe the physics of how molecular crowding can influence membrane bending and discuss the implications for other cellular processes, such as sorting of glycosylphosphatidylinositol-anchored proteins (GPI-APs) and production of intraluminal vesicles