The term
macromolecular assembly (MA) refers to massive chemical structures such as
viruses and non-biologic
nanoparticles, cellular
organelles and
membranes and
ribosomes, etc. that are complex mixtures of
polypeptide,
polynucleotide,
polysaccharide or other polymeric
macromolecules. They are generally of more than one of these types, and the mixtures are defined spatially (i.e., with regard to their chemical shape), and with regard to their underlying chemical composition and
structure.
Macromolecules are found in living and nonliving things, and are composed of many hundreds or thousands of
atoms held together by
covalent bonds; they are often characterized by repeating units (i.e., they are
polymers). Assemblies of these can likewise be biologic or non-biologic, though the MA term is more commonly applied in biology, and the term
supramolecular assembly is more often applied in non-biologic contexts (e.g., in
supramolecular chemistry and
nanotechnology). MAs of macromolecules are held in their defined forms by
non-covalent intermolecular interactions (rather than covalent bonds), and can be in either non-repeating structures (e.g., as in the
ribosome (image) and
cell membrane architectures), or in repeating linear, circular, spiral, or other patterns (e.g., as in
actin filaments and the
flagellar motor, image). The process by which MAs are formed has been termed
molecular self-assembly, a term especially applied in non-biologic contexts. A wide variety of physical/biophysical, chemical/biochemical, and computational methods exist for the study of MA; given the scale (molecular dimensions) of MAs, efforts to elaborate their composition and structure and discern mechanisms underlying their functions are at the forefront of modern structure science.