Dinamika i struktura otopina soli deoksiribonukleinske kiseline

doctoral thesis

• Title: Dinamika i struktura otopina soli deoksiribonukleinske kiseline : utjecaj valencije protuiona
• Title (english): Dynamics and strucutre of deoxyribonucleic acid salt solutions : influence of counterion valency
• Author: Danijel Grgičin
• Mentor: Tomislav Vuletić (mentor)
• Committee member: Mario Basletić (predsjednik povjerenstva)
• Committee member: Sanja Dolanski-Babić (član povjerenstva)
• Committee member: Nenad Pavin (član povjerenstva)
• Granter: University of Zagreb; Faculty of Science; (Department of Physics); Zagreb
• Defense date and country: 2015-07-25, Croatia
• Scientific / art field, discipline and subdiscipline: NATURAL SCIENCES; Physics
• Universal decimal classification (UDC): 53 - Physics

Abstract

Problem raspodjele protuiona u blizini poliiona je u fizici polielektrolita (PE) uočen još 1950-tih godina. Protuioni su podijeljeni u slobodne i Manning kondenzirane, a teorije uglavnom pokušavaju interpretirati mjerenja osmotskog tlaka. U svome radu koristio sam konduktometriju, dielektričnu spektroskopiju (DS) i raspršenje X-zraka u male kutove (engl. SAXS) kako bih istražio strukturu i dinamiku, pa tako i raspodjelu protuiona jakog PE, deoksiribonukleinske kiseline (DNA) i slabog PE, hijaluronske kiseline (HA) u rasponu koncentracija c=0.01-10 mM. U čistim vodenim otopinama PE, mjerenja DS daju κ širinu potencijalne jame poliiona – tj. prostorno protezanje atmosfere protuiona koje je 2π puta manje nego SAXSom određena udaljenost između poliiona. Drugim riječima, povećanjem koncentracije PE širina potencijalne jame κ se smanjuje. S dodanom soli širina jame ovisi pak o ionskoj jakosti otopine. Stoga smo zaključili i kako je promjena za čiste vodene otopine uzrokovana promjenom koncentracije protuiona, a ne promjenom razmaka poliiona. Nadalje, konduktometrijom je uočen porast ekvivalentne vodljivosti Λ sa sniženjem c, i za razrijeđene DNA i za polurazrijeđene DNA i HA otopine što interpretiramo smanjenjem udjela protuiona u blizini poliiona, što efektivno povećava naboj poliiona pa stoga i Λ. Naime, slabi kondenziranje Manning protuiona zbog pojačanog utjecaja entropije na niskim c. I κ i Λ bi trebali ovisiti o valenciji protuiona, što smo i potvrdili mjerenjima s Na^+ i Mg^2+ protuionima. Manning teorija za HA ne predviđa kondenzaciju protuiona (za razliku od DNA) pa ne bi trebalo biti uočenog efekta na Λ. Moguće je da entropija pri niskim koncentracijama mijenja i efektivni naboj HA. Trenutni teorijski modeli pokrivaju samo razrijeđene otopine, ali se kvalitativno slažu s našim rezultatima.

Abstract (english)

The counterion distribution problem in vicinity of poliions are recognized in polyelectrolyte (PE) physics since 1950‘s. Theories mainly interpret osmotic measurement. In this work I have used conductometry, dielectric spectrometry (DS) and small angle X-ray scattering (SAXS) in order to probe structure and dynamics, as well as counterion distribution around strong PE, deoxyribonucleic acid (DNA) and weak PE, hyaluronic acid (HA) in the concentration interval c = 0.01 − 10 mM. For no added salt PE solutions DS measurements provide the size of the counterion atmosphere κ, i.e. spatial extension of counterion atmosphere which is 2π times shorter than distance between polyions determined from SAXS. In other words, by increasing PE concentration the size of the counterion atmosphere κ shrinks. In added salt solutions κ depends on solution ionic strength. On that basis we conclude that for no added salt solution the change is also caused by variations of counterion concentration and not by distance between poliions. In conductometry we observed increase in equivalent conductivity Λ by decreasing c for dilute DNA and for semidilute DNA and HA solutions which we interpreted with decrease of number of counterions in polyion vicinity which effectively increase polyion charge, i.e. Λ. Shortly, there are less Manning condensed counterions due to entropy at those low concentracion. Both κ and Λ should depend on counterion valency which we shown with Na^+ and Mg^2+ counterions. Manning theory does not predict counterion condensation for HA (as opposed to DNA), i. e. the observed effect on Λ should not appear. Maybe entropy on low concentration changes effective charge on HA. The current theoretical models for dilute solutions qualitatively agrees with our results.

• Keywords: polielektroliti; raspodjela protuiona; osmotski koeficijent; Manning kondenzirani protuioni; širina protuionske atmosfere; električna vodljivost polielektrolita
• Keywords (english): polyelectrolytes; counterion distribution; osmotic coefficient; Manning condensed counterions; size of counterion atmosphere; electrical conductivity of polyelectrolytes
• Language: croatian
• URN:NBN: urn:nbn:hr:217:656374
• Study programme: Title: Physics; Study programme type: university; Study level: postgraduate; Academic / professional title: doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika (doktor/doktorica znanosti, područje prirodnih znanosti, polje fizika)
• Type of resource: Text
• Extent: 119 str.
• File origin: Born digital
• Access conditions: Open access
• Created on: 2017-08-21 12:31:22