Vpliv površinsko aktivnih snovi na agregacijsko stanje govejega serumskega albumina

Longar, Špela (author), Hribar Lee, Barbara (mentor), Brudar, Sandi (comentor)

Proteini so občutljivi na spremembe kemijskega okolja, ki lahko vpliva na njihovo konformacijo, stabilnost in agregacijsko stanje. Zelo pomembne so interakcije proteinov s površinsko aktivnimi snovmi, saj lahko proteine stabilizirajo, povzročijo konformacijske preureditve ali tvorijo komplekse in agregate. V diplomski nalogi sem raziskovala vpliv različnih koncentracij anionskega surfaktanta natrijevega dodecil sulfata (SDS) in neionskega surfaktanta Triton X-100 na agregacijsko stanje in sekundarno strukturo govejega serumskega albumina (BSA). Spremljali smo spremembe hidrodinamičnega radija in porazdelitve velikosti delcev z metodo dinamičnega sipanja svetlobe, spremembe v sekundarni strukturi proteina pa s cirkularnim dikroizmom v daljnem UV-območju. Deleže posameznih elementov sekundarne strukture smo ocenili s programom BeStSel. Rezultati so pokazali, da so pri nizkih koncentracijah Tritona X-100 vrednosti hidrodinamičnega radija in CD-spektri večinoma podobni kontrolnemu vzorcu, kar pomeni, da ni prišlo do porušitve α-vijačne strukture BSA. Pri 0,01 % Tritona X-100 je bil opažen nekoliko večji in bolj raznolik hidrodinamični radij, kar je nakazovalo na vezavo surfaktanta na protein. Pri 0,05 % in 0,1 % so spektri kazali na ohranjeno α-vijačno ogrodje, BeStSel rezultati pa na povečanje α-vijačnic in možen stabilizacijski učinek. Pri 0,5 % Tritona X-100 se je hidrodinamični radij povečal, vendar sekundarne strukture zaradi optičnih motenj ni bilo mogoče oceniti. Pri najnižjih koncentracijah SDS so bili rezultati podobni, hidrodinamični radij je bil primerljiv s kontrolo. Povišan delež α-vijačnih struktur je kazal na stabilizacijsko delovanje surfaktanta. Pri 1 mM SDS so se pojavile izrazitejše spremembe hidrodinamičnega radija in CD spektra. Pri 5 in 10 mM SDS se je radij še dodatno povečal, delež α-vijačnic pa zmanjšal, kar je bilo skladno z nastankom kompleksov BSA in SDS ter delno denaturacijo proteina. Interakcije Tritona X-100 z BSA so delovale pretežno stabilizacijsko, medtem ko je SDS pokazal prehodno stabilizacijsko delovanje pri najnižjih koncentracijah in z višanjem koncentracije prešel na delno denaturacijo proteina. Vpliv površinsko aktivnih snovi na agregacijsko stanje, strukturo in delovanje proteinov je torej odvisen od njihove vrste, koncentracije in mehanizma interakcije s proteini.

• Language: Slovenian
• Keywords: površinsko aktivne snovi, hidrodinamični radij, goveji serumski albumin, natrijev dodecil sulfat, Triton X-100, sekundarna struktura proteina
• Work type: Bachelor thesis/paper
• Organization: FKKT - Faculty of Chemistry and Chemical Technology
• Year: 2026
• PID: 20.500.12556/RUL-186625
• Publication date in RUL: 03.09.2026

Secondary language

• Language: English
• Title: The effect of surfactants on the aggregation state of bovine serum albumin

Abstract

Proteins are sensitive to changes in their chemical environment, which can affect their conformation, stability, and aggregation state. Interactions between proteins and surfactants are particularly important because surfactants can stabilize proteins, induce conformational rearrangements, or promote the formation of complexes and aggregates. In this thesis, we investigated the effects of different concentrations of the anionic surfactant sodium dodecyl sulfate (SDS) and the nonionic surfactant Triton X-100 on the aggregation state and secondary structure of bovine serum albumin (BSA). Changes in the hydrodynamic radius and particle-size distribution were monitored using dynamic light scattering, while changes in protein secondary structure were examined using far-UV circular dichroism. The proportions of individual secondary-structure elements were estimated using the BeStSel program. The results showed that, at low Triton X-100 concentrations, the hydrodynamic radius values and CD spectra were generally similar to those of the control sample, indicating that the α-helical structure of BSA was largely preserved. At 0.01 % Triton X-100, a slightly larger and more variable hydrodynamic radius was observed, suggesting surfactant binding to the protein. At 0.05% and 0.1 %, the spectra indicated preservation of the α-helical framework, while the BeStSel results suggested an increased α-helical content and possible structural stabilization. At 0.5 % Triton X-100, the hydrodynamic radius increased; however, the secondary structure could not be reliably evaluated because of optical interference. Similar results were obtained at the lowest SDS concentrations, where the hydrodynamic radius was comparable to that of the control sample. The increased estimated proportion of α-helical structures suggested a possible stabilizing effect of the surfactant. At 1 mM SDS, more pronounced changes in the hydrodynamic radius and CD spectrum were observed. At 5 and 10 mM SDS, the radius increased further, while the proportion of α-helices decreased. These findings were consistent with the formation of BSA–SDS complexes and partial protein denaturation. Interactions between Triton X-100 and BSA were predominantly stabilizing, whereas SDS exhibited a stabilizing effect at the lowest concentrations and induced partial protein denaturation as its concentration increased. The effects of surfactants on the aggregation state, structure, and function of proteins therefore depend on the type and concentration of the surfactant, as well as on its mechanism of interaction with the protein.

• Keywords: surfactants, hydrodynamic radius, bovine serum albumin, sodium dodecyl sulfate, Triton X-100, protein secondary structure