Model diobenog vretena određen momentima sila i silama

master's thesis

• Title (english): Mitotic spindle model determined by torques and forces
• Author: Zvonimir Boban
• Mentor: Nenad Pavin (mentor)
• Committee member: Nenad Pavin (predsjednik povjerenstva)
• Committee member: Hrvoje Buljan (član povjerenstva)
• Committee member: Mirko Planinić (član povjerenstva)
• Committee member: Vito Despoja (član povjerenstva)
• Committee member: Danko Radić (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2017-06-30, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics

Abstract

Diobeno vreteno je stanična struktura koja se formira za vrijeme stanične diobe kako bi se genetski materijal jednoliko podijelio medu stanicama kćeri. Sile igraju ključnu ulogu u funkcioniranju vretena, sudjelujući u pomicanju njegovih dijelova i održavanju oblika. Unatoč tome, te sile nije lako odrediti korištenjem dosadašnjih eksperimentalnih metoda pa se stoga o njima jako malo zna. Kako bismo riješili ovaj problem, proučavamo oblik vretena i izvlačimo zaključke o silama na temelju poznavanja elastičnih svojstava mikrotubula. Promatranjem diobenih vretena ljudskih stanica STED superrezolucijskom mikroskopijom, vidjeli smo da svežnjevi mikrotubula nalikuju oblicima slova C i S. Uz pomoć konfokalne mikroskopije, snimana su vretena orijentirana približno okomito na ravninu snimanja te je otkriveno da posjeduju kiralnost. Pokazano je da je kiralnost lijeva sa srednjim helicitetom svežnjeva od oko -1 stupanj/μm. Kako bi se perturbirao iznos heliciteta, mijenjana je aktivnost motornog proteina kinezina 5. Razvijen je i teorijski model u kojemu je svežanj mikrotubula opisan kao tanki elastični štap. Kako bi se objasnila eksperimentalna opažanja, model predviđa postojanje momenata sila uz same sile. Zaključujemo kako uz sile, oblik diobenog vretena određuju i momenti sila generirani od strane motornih proteina.

Abstract (english)

The mitotic spindle is a micromachine formed during cell division to ensure even distribution of genetic material amongst daughter cells. Forces in the spindle play a key role in its functioning, by driving movement of its constituents and maintaining its shape. However, these forces are not easily accessible by current experimental techniques and, therefore, remain to a large extent unknown. To tackle this problem, we study spindle shape and infer forces from elastic properties of microtubules. We used STED super-resolution microscopy to image human cell spindles and found that microtubule bundles resemble C and S letter shapes. By using confocal imaging of spindles oriented roughly perpendicular to the imaging plane, we show that they possess chirality. We found that chirality is left-handed with an average bundle helicity around -1 deg/μm. To perturb the twisting moment in our spindles, we altered the activity of motor protein kinesin-5 (Eg5/Kif11). A theoretical model is developed with a microtubule bundle described as an elastic slender rod, which suggests that a torque is required to generate the observed helical shapes. We conclude that torques generated by motor proteins, in addition to forces, exist in the spindle and determine its shape.

• Keywords: Diobeno vreteno; svežnjevi mikrotubula; kiralnost; helicitet; sile; momenti sila; motorni proteini; kinezin 5; savijanje; uvijanje; STED; konfokalna mikroskopija; vertikalna vretena; praćenje; FCPT; STLC
• Keywords (english): Mitotic spindle; microtubule bundles; chirality; helicity; forces; torques; motor proteins; kinesin 5; bending; twisting; STED; confocal microscopy; vertical spindles; tracking; FCPT; STLC
• Language: croatian
• URN:NBN: urn:nbn:hr:217:892991
• Study programme: Title: Physics; specializations in: Research; Course: Research; Study programme type: university; Study level: integrated undergraduate and graduate; Academic / professional title: magistar/magistra fizike (magistar/magistra fizike)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Open access; Embargo expiration date: 2019-06-30
• Created on: 2017-07-07 14:00:22