Molecular Electroporation and the Transduction of Oligoarginines

Certain short polycations, such as TAT and polyarginine, rapidly pass through the plasma membranes of mammalian cells by an unknown mechanism called transduction as well as by endocytosis and macropinocytosis. These cell-penetrating peptides (CPPs) promise to be medically useful when fused to biologically active peptides. I offer a simple model in which one or more CPPs and the phosphatidylserines of the inner leaflet form a kind of capacitor with a voltage in excess of 180 mV, high enough to create a molecular electropore. The model is consistent with an empirical upper limit on the cargo peptide of 40--60 amino acids and with experimental data on how the transduction of a polyarginine-fluorophore into mouse C2C12 myoblasts depends on the number of arginines in the CPP and on the CPP concentration. The model makes three testable predictions.Comment: 15 pages, 5 figure

Ribosome recycling induces optimal translation rate at low ribosomal availability

Funding statement The authors thank BBSRC (BB/F00513/X1, BB/I020926/1 and DTG) and SULSA for funding. Acknowledgement The authors thank R. Allen, L. Ciandrini, B. Gorgoni and P. Greulich for very helpful discussions and careful reading of the manuscript.Peer reviewedPublisher PD

Bidirectional transport on a dynamic lattice

Bidirectional variants of stochastic many particle models for transport by molecular motors show a strong tendency to form macroscopic clusters on static lattices. Inspired by the fact that the microscopic tracks for molecular motors are dynamical, we study the influence of different types of lattice dynamics on stochastic bidirectional transport. We observe a transition toward efficient transport (corresponding to the dissolution of large clusters) controlled by the lattice dynamics.Comment: 5 pages, 5 figure

'n Vertalende vakwoordeboek van politieke terme

Staatkundige en Verwante Terminologie wat in 1990 verskyn het, is aansienlik deur die Sentrum vir Politieke en Verwante Terminologie in Suider-Afrikaanse Tale (SEPTSA) hersien en bygewerk ten einde dit as die Nuwerwetse Politieke Woordeboek te publiseer. Die verskillende stadia in die hersiening en uitvoering van die projek word bespreek. Die hersiening bevat heelwat meer terme as die vorige publikasie en verskeie bylaes word ingesluit. Aandag word gegee aan die waarde van die tweetalige vertalende en die beplande meertalige verklarende politiekewetenskap-peprojek binne die Suid-Afrikaanse en wêreldkonteks. Nuutskeppings en verskeie probleemterme word bespreek, spelling- en transliterasieprobleme wat by die verafrikaansing van ontleende terme ontstaan het, word behandel, en winste uit sowel die inheemse tale as uit vreemde tale word beskou. 'n Oorsig word gegee van 'n verskeidenheid funksionele agtervoegsels wat baie produktief in die Nuwerwetse Politieke Woordeboek gebruik word. Die woordeboek bevat 'n aansienlike aantal afkortings vir volvorme. 'n Aanduiding word gegee van die soort afkortings wat in die woorde-boek opgeneem is. Die bylaes bygevoeg by die woordeboek word bespreek, en die artikel sluit af met 'n oorsig oor toekomsplanne. Sleutelwoorde: afkorting, akroniem, meertalige vakwoordeboek, nuut-skepping, probleemterm, term, terminologie, termskepping, tweetalige tweerigting vertalende vakwoordeboek, tweetalige vakwoordeboek, verafrikaansing, verklarende woordeboek, vertalende woordeboek, vol-vor

Model for the unidirectional motion of a dynein molecule

Cytoplasmic dyneins transport cellular organelles by moving on a microtubule filament. It has been found recently that depending on the applied force and the concentration of the adenosine triphosphate (ATP) molecules, dynein's step size varies. Based on these studies, we propose a simple model for dynein's unidirectional motion taking into account the variations in its step size. We study how the average velocity and the relative dispersion in the displacement vary with the applied load. The model is amenable to further extensions by inclusion of details associated with the structure and the processivity of the molecule.Comment: 10 pages, 5 figure

Terminology development at tertiary institutions: A South African perspective

There is a dire need in South Africa for multilingual polythematic terminology. Currently no tertiary institution presents terminology theory and practice as a fully-fledged subject and there is also no sufficient mechanism for the training of terminologists. This situation provides tertiary institutions the opportunity to position themselves in terms of terminology training and development. Terminology centres at tertiary institutions could be of great value for language as well as all other subject-related departments. The language departments, where such terminology centres could possibly be housed, already have facilities to teach some or all of the official languages of South Africa at tertiary level. Language students could receive postgraduate (and even undergraduate) training in the theory and practice of terminology. For practical work, they could collect terminology at subject-related departments and take it to the terminology centres, where source language terms could be terminographically treated. Subject specialists (i.e. lecturers teaching different subjects) would have to be consulted when defining the concepts and would have to assist language students and their lecturers to supply term equivalents in target languages. This process would enable subject-related and language departments to cooperate in different domains. Language and language departments would therefore become useful to different subject areas. Multilingual polythematic terms with definitions could be available to students who are not proficient in English or Afrikaans. They would therefore have access to study material in their first language. The terminology could be disseminated internally and (inter)nationally through the Internet, which would make it accessible to any other student. This process could best be managed and executed by dedicated terminology centres.Keywords: Legislation, multilingual terminology, polythematic terminology, source language, standardisation, target language, terminography, terminology, terminology centre, terminology development, terminology trainingTerminologieontwikkeling aan tersiêre instansies: 'n Suid-Afrikaanse perspektiefDaar bestaan in Suid-Afrika 'n groot behoefte aan meertalige terminologie op verskeie vakgebiede. Tans bied geen tersiêre instansie terminologieteorie en -praktyk as volwaardige vak aan nie en daar is nie 'n doeltreffende meganisme waarvolgens terminoloë opgelei kan word nie. Hierdie situasie skep die geleentheid vir tersiêre instansies om hulself te posisioneer ten opsigte van terminologieopleiding en -ontwikkeling. Terminologiesentra aan tersiêre instansies sal vir taal- sowel as alle ander vakgerigte departemente van onskatbare waarde wees. Die taaldepartemente, waar sodanige sentra waarskynlik gehuisves sou kon word, beskik reeds oor fasiliteite om sommige of alle amptelike tale van Suid-Afrika op tersiêre vlak aan te bied. Taalstudente kan nagraadse (en selfs voorgraadse) opleiding kry in terminologieteorie en -praktyk. As praktiese werk sou hulle terminologie by vakgerigte departemente kon gaan versamel en na die sentra neem waar die brontaalterme terminografies hanteer kan word. Vakkundiges (bv. lektore wat vakke aanbied) sal met die definiëring van konsepte behulpsaam moet wees en sal saam met die taalstudente en -dosente vertaalekwivalente in doeltale moet verskaf. Dié proses sal meebring dat vakkundiges en taalkundiges oor vakgrense heen saamwerk. Dit sal daartoe lei dat taal en taaldepartemente vir ander vakterreine van waarde sal raak. Meertalige vakgerigte terme met definisies sal beskikbaar wees vir studente wat nie Engels of Afrikaans magtig is nie. Hulle sal dus toegang tot studiemateriaal in hul eerste taal kan kry. Die terminologie kan intern deur die tersiêre instansies en (inter)nasionaal deur die Internet versprei word, wat dit toeganklik sal maak vir enige ander student. Hierdie proses kan ten beste deur doelgerigte terminologiesentra beheer en uitgevoer word.Sleutelwoorde: Brontaal, doeltaal, meertalige terminologie, standaardisering, terminografie, terminologie, terminologieopleiding, terminologieontwikkeling, terminologiesentrum, vakgerigte terminologie, wetgewin

The Afrikaans Orthographic Rules as Guide for Other South African Languages*

The spelling and orthographic rules of a language are very important for compilers of general and technical dictionaries. When compiling a dictionary, the lexicographers and terminographers should adhere to these rules. The word-forming principles of a language form part of these rules, and new terms can only be coined in a given language if the spelling and orthographic rules of the language are followed.In this article work on the rules of Afrikaans spelling and orthography, by and large, is reported. It is hoped that some of the lessons learned in the process could serve as guidelines for parallel processes of the standardisation of the spelling and orthographies of the other South African languages. With the establishment of the National Language Body for Afrikaans (NLBA) of the Pan South African Language Board (PanSALB), it was decided that the members of the Taalkommissie (Language Commission) of the Suid-Afrikaanse Akademie vir Wetenskap en Kuns (SAAWK) (South African Academy for Science and the Arts) would become members of the NLBA. These members then became the Technical Committee for Standardisation (TC Standardisation). Since its establishment, the members of the Taalkommissie cum TC for Standardisation (Commission) continued with their work on the standardisation of the spelling and orthographic rules for Afrikaans. Along with work on spelling and orthography, the long-term objectives set by the Commission are, inter alia, the conversion and adaptation of the Afrikaanse Woordelys en Spelreëls (AWS) to an electronic format to be made available in an electronic version (e-book) and online, as well as a standard grammar for Afrikaans to be compiled for international access on the Internet.The AWS is a resource compiled by the Commission to assist users of Afrikaans in writing the standard variety of the language. The AWS explains the ground rules of the Afrikaans spelling and orthographic conventions. The basic rules are provided in simplified language.No language is static, and there are always language changes to be taken into account. The vocabulary and pronunciation of a dynamic language could change over a period of time. These changes should be reflected in the spelling and orthographic system of the language.The article addresses issues such as the front matter of the AWS, spelling and orthographic principles and rules, and the back matter (i.e. a list of abbreviations, a list of international place names, transliteration table,  etc.). Although the AWS is not a dictionary, it also contains a word list. Words which present spelling problems, neologisms and items requiring recognition as part of the Afrikaans vocabulary are some of the categories considered for inclusion in this list.In 2004 the NLBs of the other nine official African languages started with the revision of the spelling and orthographic rules of these languages. The first editions were published by PanSALB in 2008. No revisions have been compiled since. The AWS could serve as example of what could be done for the other African languages and even the Khoe and San languages.Keywords: Alphabet, language change, lexicographer, lexicography, orthography, simplified language, spelling, standardisation, terminographers, terminography, transliteratio

The African Association for Lexicography: After Ten Years

This year it has been ten years since the establishment of AFRILEX. After an expla-nation of what led to its forming, this article gives a short overview of its composition and activi-ties. Keywords: african association for lexicography (afrilex), african lan-guages association of south africa (alasa), bureau of the woordeboek van die afrikaanse taal (wat), dictionary of south african english (dsae), linguistic association of southern africa (lssa), national lexicography units (nlus), pan south african language board (pansalb

Microtubule length distributions in the presence of protein-induced severing

Microtubules are highly regulated dynamic elements of the cytoskeleton of eukaryotic cells. One of the regulation mechanisms observed in living cells is the severing by the proteins katanin and spastin. We introduce a model for the dynamics of microtubules in the presence of randomly occurring severing events. Under the biologically motivated assumption that the newly created plus end undergoes a catastrophe, we investigate the steady state length distribution. We show that the presence of severing does not affect the number of microtubules, regardless of the distribution of severing events. In the special case in which the microtubules cannot recover from the depolymerizing state (no rescue events) we derive an analytical expression for the length distribution. In the general case we transform the problem into a single ODE that is solved numerically.Comment: 9 pages, 4 figure