The e ect of cytochrome c on the melting transition of charged model lipid-membranes using FTIR-spectroscopy

The biological membrane has historically never played a very dominant role in biochemistry. It has merely been conceived as a barrier that hinds the cellinteriors from di using. In Hodgkin and Huxley 's model of nerve signaling it works as a capaciter. In this thesis I examine the e ect of the peripheral protein cytochrome c on a membrane consisting of the charged lipid DMPG. I will show that the heatcapacity of the membrane as a function of temperature is changed with the addition of cytochrome c. The heatcapacity peaks around the meltingpoint for the membrane but the peak of the heatcapacity is lowered, broadened and shifted to a higher temperature when cytochrome c i added. Hence the meltingpoint is altered. The approach of this thesis is thermodynamical and the measurements are with FTIRspectroscopy. Resumé Biologiske membraner har historisk set aldrig spillet en central rolle i biokemien. Den er blevet opfattet som en barriere, der skulle forhindre cellens dele i at difundere væk. I Hodgkin and Huxley 's model for nervesignalering fungerer den som en capacitor. I denne opgave vil jeg undersøge hvordan over adeproteinet cytochrom c indvirker på en membran bestående af den ladede lipid DMPG. Jeg vil vise at varmekapaciteten af en membran som funktion af temperaturen ændrer sig når der er cytochrome c på den. Varmekapaciteten topper når membranen smelter men kurven bliver lavere, bredere og forskubbes til en højere temperatur når cytochrome c bliver tilsat. Derved er også smeltepunktet forskudt. Tilgangen i denne opgave er termodynamisk og forsøgene er udført ved FTIR-spektroskopi.