Heterogeneity and Persistence Length in Human Ocular Mucins

Atomic force microscopy (AFM) has been used to investigate the heterogeneity and flexibility of human ocular mucins and their subunits. We have paid particular attention, in terms of theory and experiment, to the problem of inducing the polymers to assume equilibrium conformations at a surface. Muci...

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Bibliographic Details
Published in:Biophysical journal 2002-09, Vol.83 (3), p.1661-1670
Main Authors: Round, A.N., Berry, M., McMaster, T.J., Stoll, S., Gowers, D., Corfield, A.P., Miles, M.J.
Format: Article
Language:English
Subjects:
Air
Conjunctiva - metabolism
Conjunctiva - ultrastructure
DNA - metabolism
Humans
Image Processing, Computer-Assisted
Microscopy, Atomic Force
Models, Theoretical
Mucins - chemistry
Mucins - physiology
Mucous membrane
Nickel - pharmacology
Nucleic Acid Conformation
Physics
Plasmids - metabolism
Polymers
Polymers - chemistry
Protein Conformation
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Summary:Atomic force microscopy (AFM) has been used to investigate the heterogeneity and flexibility of human ocular mucins and their subunits. We have paid particular attention, in terms of theory and experiment, to the problem of inducing the polymers to assume equilibrium conformations at a surface. Mucins deposited from a buffer containing Ni 2+ ions adopt extended conformations on mica akin to those observed for DNA under similar conditions. The heterogeneity of the intracellular native mucins is evident from a histogram of contour lengths, reflecting, in part, the diversity of mucin gene products expressed. Reduction of the native mucin with dithiothreitol, thereby breaking the S S bonds between cysteine residues, causes a marked reduction in polymer length. These results reflect the modes of transport and assembly of newly synthesized mucins in vivo. By modifying the worm-like chain model for applicability to two dimensions, we have confirmed that under the conditions employed mucin adsorbs to mica in an equilibrated conformation. The determined persistence length of the native mucin, 36 nm, is consistent with that of an extended, flexible polymer; such characteristics will influence the properties of the gels formed in vivo.
ISSN:0006-3495
1542-0086
DOI:10.1016/S0006-3495(02)73934-9