Pixel-based analysis of FRAP data with a general initial bleaching profile
Artikel i vetenskaplig tidskrift, 2010

Jonasson et al. (2008), we presented a new pixel-based maximum likelihood framework for the estimation of diffusion coefficients from data on fluorescence recovery after photobleaching (FRAP) with confocal laser scanning microscopy (CLSM). The main method there, called the Gaussian profile method below, is based on the assumption that the initial intensity profile after photobleaching is approximately Gaussian. In the present paper, we introduce a method, called the Monotone profile method, where the maximum likelihood framework is extended to a general initial bleaching profile only assuming that the profile is a non-decreasing function of the distance to the bleaching centre. The statistical distribution of the image noise is further assumed to be Poisson instead of normal, which should be a more realistic description of the noise in the detector. The new Monotone profile method and the Gaussian profile method are applied to FRAP data on swelling of super absorbent polymers (SAP) in water with a Fluorescein probe. The initial bleaching profile is close to a step function at low degrees of swelling and close to a Gaussian profile at high degrees of swelling. The results obtained from the analysis of the FRAP data are corroborated with NMR diffusometry analysis of SAP with a polyethylene glycol probe having size similar to the Fluorescein. The comparison of the Gaussian and Monotone profile methods is also performed by use of simulated data. It is found that the new Monotone profile method is accurate for all types of initial profiles studied, but it suffers from being computationally slow. The fast Gaussian profile method is sufficiently accurate for most of the profiles studied, but underestimates the diffusion coefficient for profiles close to a step function. We also provide a diagnostic plot, which indicates whether the Gaussian profile method is acceptable or not.

isotonic regression

CLSM

Diffusion

maximum likelihood

super absorbent

FRAP

fluorescence recovery

MLE

Författare

Jenny Jonasson

SuMo Biomaterials

Göteborgs universitet

Chalmers, Matematiska vetenskaper, matematisk statistik

Joel H Hagman

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

SuMo Biomaterials

Niklas Lorén

SuMo Biomaterials

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

Diana Bernin

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

SuMo Biomaterials

Magnus Nydén

Chalmers, Kemi- och bioteknik, Teknisk ytkemi

SuMo Biomaterials

Mats Rudemo

Göteborgs universitet

Chalmers, Matematiska vetenskaper, matematisk statistik

Journal of Microscopy

0022-2720 (ISSN) 1365-2818 (eISSN)

Vol. 239 2 142-153

Ämneskategorier

Kemiteknik

Sannolikhetsteori och statistik

DOI

10.1111/j.1365-2818.2009.03361.x

Mer information

Skapat

2017-10-07