ABSTRACT
Magnetic Particle Imaging (MPI) is an emerging tomographic imaging technology that detects magnetic nanoparticle tracers by exploiting their non-linear magnetization properties. In order to predict the behavior of nanoparticles in an imager, it is possible to use a non-imaging MPI relaxometer or spectrometer to characterize the behavior of nanoparticles in a controlled setting. In this paper we explore the use of ferrohydrodynamic magnetization equations for predicting the response of particles in an MPI relaxometer. These include a magnetization equation developed by Shliomis (Sh) which has a constant relaxation time and a magnetization equation which uses a field-dependent relaxation time developed by Martsenyuk, Raikher and Shliomis (MRSh). We compare the predictions from these models with measurements and with the predictions based on the Langevin function that assumes instantaneous magnetization response of the nanoparticles. The results show good qualitative and quantitative agreement between the ferrohydrodynamic models and the measurements without the use of fitting parameters and provide further evidence of the potential of ferrohydrodynamic modeling in MPI.
ABSTRACT
The amino acid sequence of gamma-crystallin (fraction II) from calf lens has been determined; this indicates it to be a single-chain polypeptide of 165 amino acid residues.
Subject(s)
Crystallins/analysis , Amino Acid Sequence , Amino Acids/analysis , Animals , Cattle , Chromatography, Paper , Cyanogen Bromide , Electrophoresis , Peptides/analysis , TrypsinSubject(s)
Crystallins/analysis , Animals , Cattle , Chromatography, Ion Exchange , Formates , Hydrogen Peroxide , Oxidation-Reduction , Peptides , Protein Conformation , TrypsinSubject(s)
Viomycin , Chemical Phenomena , Chemistry , Guanidines , Hydrogen-Ion Concentration , Hydrolysis , Peptides , Pigments, Biological , Spectrum Analysis , UreaABSTRACT
The amino acid sequences around the cysteine residues in the lens protein, gamma-crystallin, were studied. Fraction II of the gamma-crystallin from calf lens (Björk, 1964) was used. The protein was oxidized with performic acid and then hydrolysed with trypsin. Six peptides containing cysteic acid were isolated. One of the peptides contained three residues of cysteic acid and the others contained one residue of cysteic acid. We conclude that there are eight unique residues of cysteic acid in the oxidized protein. Amino acid analysis suggests that there are also eight residues of cysteic acid in the molecule, which thus contains only one polypeptide chain.
