Biomedical Engineering Reference
In-Depth Information
biological function. Many of the most important molecular processes in the cell such as DNA
replication are carried out by large molecular machines that are built from a large number of
protein components organised by their protein-protein interactions [2,3]. Protein interactions
have been studied from the perspectives of biochemistry [4],quantum chemistry [5],
molecular dynamics [6], signal transducton [7], and other metabolic or genetic/epigenetic
networks. Indeed, protein-protein interactions are at the core of the entire interactomic[8]
system of any living cell. The interactions between proteins are important for the majority of
biological functions. For example, signals from the exterior of a cell are mediated to the
inside of that cell by protein-protein interactions of the signaling molecules [9]. This process,
called signal transduction plays a fundamental role in many biological processes and in many
diseases (e.g. cancers). Proteins might interact for a long time to form part of a protein
complex, a protein may be carrying another protein (for example, from cytoplasm to nucleus
or vice versa in the case of the nuclear pore [10] (importins), or a protein may interact briefly
with another protein just to modify it (for example, a protein kinase will add a phosphate to a
target protein [11]). This modification of proteins can itself change protein-protein
interactions. For example, some proteins with SH
2
domains only bind to other proteins when
they are phosphorylated on the aminoacid tyrosine while bromodomains specifically
recognise acetylated lysines [12]. Protein-protein interactions are of central importance for
virtually every process in a living cell. Information about these interactions improves our
understanding of diseases and can provide the basis for new therapeutic approaches. Protein
mixtures may exist in molecular dispersed and colloidal dispersed states depending on the
properties of the individual proteins, the composition of the mixtures and the conditions in
which the mixtures are obtained. Colloidal protein dispersions play a pivotal role in our
everyday life and can be exploited for the efficient production of food [13]. The interaction
between proteins has been extensively investigated, in particular for the modulation of living
processes in plant and animal cells, These interactions may result in the formation of water-
soluble complexes, complex coacervation, formation of amorphous precipitates, stabilised by
diferent type of bonds , or in the thermodynamic incompatibility of the macromolecules
leading to liquid-liquid phase separation. Protein-protein interaction occur in many physical
and chemical processes and affect nutritional and organoleptic quality of food products during
manufacture and storage. Most studies, to date, display interesting and technologically useful
properties produced by interactions including: enchanced gelation properties by synergistic
interactions, phase separation and new textural properties and aggregation of oppositevily
charged proteins [14]. Clearly, a knowledge of protein interaction can lead to a better
understanding of biochemical changes in food products during processing and storage such as
aggregation of proteins in fish leading to toughening on frozen storage [14]. Furthemore, an
understanding of the effect of protein structure on protein-protein interactions, for example, of
smooth and skeletal muscle proteins, permit the manipulation of protein side chains in order
to enhance gelation properties. However, data are lacking for a quantitative understanding of
how structural features of the proteins, as well as the diferent physico-chemical factors affect
molecular, and aggregation properties of complexes. The aim of this study to characterize
intermcromolecular interactions, structure and aggregation in the system containing a small
globular protein and a relatively large protein with a conformationally variable chain using
dynamic light scattering, differential scanning calorimetry, circular dichroism, fluorescence,
and absorption measurements. It uses the dilute and semidilute system water/bovine serum
albumin (BSA)/acid gelatin as a model. The molecular weight, charge, structure and
Search WWH ::
Custom Search