PROBING THE MICROSTRUCTURE OF BIOMATERIALS WITH POSITRONS Doctoral Dissertation

نویسندگان

  • Petri Sane
  • Antero Sane
  • Martti Puska
  • Filip Tuomisto
چکیده

OF DOCTORAL DISSERTATION AALTO UNIVERSITY SCHOOL OF SCIENCE AND TECHNOLOGY P.O. BOX 11000, FI-00076 AALTO http://www.aalto.fi Author Petri Antero Sane Name of the dissertation Probing the microstructure of biomaterials with positrons Manuscript submitted 15.6.2010 Manuscript revised 15.9.2010 Date of the defence 8.10.2010 Monograph Article dissertation (summary + original articles) Faculty Faculty of Information and Natural Sciences Department Department of Applied Physics Field of research Experimental Positron Physics Opponent(s) Dr. Alan Drew, Queen Mary University of London Supervisor Prof. Martti Puska Instructor Doc. Filip Tuomisto Abstract Voids in biological membranes are vital to the diffusion characteristics of the membranes and as such information gained from e.g. void sizes elucidates the understanding of the functionality of the membrane. In this thesis the focus is on lipid bilayers, a type of membrane that exists in almost all organisms as a diffusion barrier surrounding the cells. The lipid bilayer consists of hydrophilic and hydrophobic parts that can form the bilayer structure in aqueous solution and the structural properties of the inner core of the bilayer (aka. hydrocarbon tail area) have a strong effect on the diffusion of particles through the bilayer. One of the key elements in the bilayer structure is the distribution and size of the free volume pockets, voids. The size of the voids depend both on the lipid type, but as well as the structural parameters of the bilayer, so called phase behaviour of the bilayer structure. Positron annihilation lifetime spectroscopy is a widely used tool to characterize atomic-scale structural properties of both solid state and soft matter and as such the correlation with positron (or to be specific positronium, the bound state of positron and electron) lifetime and the size of voids in e.g. polymers has been observed. In this thesis positron annihilation lifetime spectroscopy has been applied to probe the voids in lipid bilayers in several manners: Firstly as a proof-of-concept-type of experiment reveals the feasibility of positron annihilation lifetime spectroscopy as a tool to detect subtle differences in the void sizes depending on the lipid concentration in aqueous solution, secondly it is found possible to characterize the phase transition temperature by observing the change of void sizes below and above the phase transition temperature. In addition, the effect of dopants, namely cholesterol, on the bilayer structure is studied as a function of cholesterol concentration. The feasibility of positron annihilation lifetime spectroscopy to study intact tissues in-situ is also presented in a study where the temperature-induced structural transition of mammalian lens is observed and traced down to the lipids the lens strongly consists of.

برای دانلود رایگان متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

A Comparative Study of the Defense of Nursing PhD Thesis in Iran and Top United States Universities

Background : The most important event in the doctoral course is the completion and defense of the dissertation, which leads to learning and improving the necessary skills to conduct research and improve performance in the field. Evaluating a doctoral dissertation defense program helps to identify the strengths and weaknesses of this process. Therefore, this comparative study has investigated th...

متن کامل

Textual Engagement of Native English Speakers in Doctoral Dissertation Discussion Sections

Academic writing is no longer considered an objective and impersonal form of discourse. It is now seen as an attempt involving interaction between writers and readers; hence, academics are not only required to produce texts representing external realities but also to use language to recognize, build, and exchange social relations. The present study aimed to analyze how native English speakers, ...

متن کامل

Identifying the guiding approaches of doctoral dissertations and examining the current and desirable situation from the perspective of Isfahan University students

Thesis and dissertation is one of the most important components of the higher education system and its accurate implementation leads to the increase and development of scientific production in any country. The doctoral dissertation can be examined from various aspects, one of which is to pay attention to the guidance approach and do it. Therefore, the purpose of this study is to identify the ap...

متن کامل

Probing Cortical Excitability with Transcranial Magnetic Stimulation

OF DOCTORAL DISSERTATION HELSINKI UNIVERSITY OF TECHNOLOGY P. O. BOX 1000, FI-02015 TKK http://www.tkk.fi Author Dubravko Kičić Name of the dissertation Manuscript submitted 14.4.2009 Manuscript revised 2.10.2009 Date of the defence 13.10.2009 Article dissertation (summary + original articles) Monograph Faculty Department

متن کامل

Evaluating the Evaluator: Towards understanding Feed-back, Feed-up, and Feed-forward of Moroccan Doctorate Supervisors’ Reports

Supervisor’s feedback is both a naysaying and a puzzling concern that has always tormented academics in higher education. Particularly, written feedback on pre-final or final versions of a submitted doctoral dissertation is indisputably the most significant step toward granting a doctoral student supervisee the right to defend his/her research project. It also constitutes a rich source on how s...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2010