[20190531 : Colloquium]A novel computational framework for time-dependent diffusion coefficients in cell membranes
1. 일시 : 2019년 5월 31일 (금) 오후 4시 30분 ~ 5시 30분
2. 장소 : 아산이학관 526호
3. 연사 : 강민철 (Texas A&M Univ Commerce, 수학과)
4. 제목 : A novel computational framework for time-dependent diffusion coefficients in cell membranes
5. 초록 : Diffusion of proteins and lipids in lipid membranes plays a pivotal role in almost all aspects of cellular biology including motility, exo-/endocytosis, and signal transduction. For this reason, gaining a detailed understanding of membrane structure and function has long been a major area of cell biology research. To better elucidate this structure-function relationship various tools have been developed for diffusion measurement including Fluorescence Recovery After Photobleaching (FRAP). However, due to complex cellular microenvironments, biological diffusion is often correlated over time and described by a time-dependent diffusion coefficient, D(t), although the underlying mechanisms are not fully understood. Since D(t) provides important information regarding cellular structures, such as the existence of subresolution barriers to diffusion, many efforts have been made to quantify D(t) by FRAP assuming the single power law D(t)=Γt^(α-1) where Γ and α are transport coefficient and anomalous exponent. However, currently, straightforward approaches to quantify a general form of D(t) are lacking. In this study, we develop a novel mathematical and computational framework to compute the mean square displacement of diffusing molecules and diffusion coefficient D(t) from each individual time point of confocal FRAP data without the single power law assumption. Additionally, we developed an auxiliary equation for D(t) which can readily distinguish normal diffusion and single power law anomalous diffusion from other types of anomalous diffusion directly from FRAP data. Importantly, by applying this approach to FRAP data from a variety of membrane markers, we demonstrate the single power law anomalous diffusion assumption is not enough to describe various types of D(t) of membrane proteins. Lastly, we discuss how our new approaches can be applied to other fluorescence microscopy tools such as Fluorescence Correlation Spectroscopy (FCS) and Single Particle Tracking (SPT).