Three-Dimensional Biological Structures

Organ printing is in general a computer-aided, dispenser-based, three-dimensional tissue-engineering technology directed to the construction of functional organ modules and eventually entire organs, layer-by-layer. 

A plurality of multicellular bodies can be arranged in a pattern and allowed to fuse to form an engineered tissue (37). Such three-dimensional constructs can be assembled by printing the multiceUular bodies and filler bodies. 

As a shaping device, a capillary pipette can be used that is part of a printing head of a bioprinter. 

The inclusion of extracellular matrix components, such as gelatin or fibrinogen, in the cell paste may facilitate the production of a multiceUular body in a single maturation step, because such components can promote the overaU cohesivity of the multiceUular body. 

Several examples for the preparation of multiceUular bodies and of tissue engineering have been presented in detail (37). 

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G. Forgacs, F.S. Marga, and C. Norotte, Self-assembling multicellular bodies and methods of producing a three-dimensional biological structure using the same, US Patent 8143 055, assigned to The Curators of the University of Missouri (Columbia, MO), March 27, 2012. 

A worldwide repository for the processing and distribution of three-dimensional biologic macromolecular structure data.) The Protein Kinase Resource http //pkr.sdsc.edu/html/index. shtml... 

Many biological, physical and chemical properties are clearly functions of the three-dimensional (3D) structure of a molecule. Thus, the understanding of receptor-ligand interactions, molecular properties or chemical reactivity requires not only information on how atoms are connected in a molecule (connection table), but also on their 3D structure. 

The use of porphyrinic ligands in polymeric systems allows their unique physio-chemical features to be integrated into two (2D)- or three-dimensional (3D) structures. As such, porphyrin or pc macrocycles have been extensively used to prepare polymers, usually via a radical polymerization reaction (85,86) and more recently via iterative Diels-Alder reactions (87-89). The resulting polymers have interesting materials and biological applications. For example, certain pc-based polymers have higher intrinsic conductivities and better catalytic activity than their parent monomers (90-92). The first example of a /jz-based polymer was reported in 1999 by Montalban et al. (36). These polymers were prepared by a ROMP of a norbor-nadiene substituted pz (Scheme 7, 34). This pz was the first example of polymerization of a porphyrinic macrocycle by a ROMP reaction, and it represents a new general route for the synthesis of polymeric porphyrinic-type macrocycles. 

The history of molecular biology has been a history of technological developments for determining the primary and tertiary structures of protein and nucleic acid molecules. Once the molecular structure is known, it provides clues to molecular functions. This is the principle of the structure-function relationship. Based on this principle the analysis of the amino acid sequence is performed to decipher the functional information from the sequence information. The analysis usually involves detection and prediction of empirical sequence—function relationships with additional consideration of known or predicted three-dimensional (3D) structures. Thus, the process can be represented schematically as ... 

Now we can ask what is likely to happen to the three-dimensional structure of a protein if we make a conservative replacement of one amino acid for another in the primary structnre. A conservative replacement involves, for example, substitution of one nonpolar amino acid for another, or replacement of one charged amino acid for another. Intnitively, one would expect that conservative replacements would have rather little effect on three-dimensional protein structure. If an isoleucine is replaced by a valine or leucine, the structnral modification is modest. The side chains of all of these amino acids are hydrophobic and will be content to sit in the molecnlar interior. This expectation is borne out in practice. We have noted earlier that there are many different molecnles of cytochrome c in nature, all of which serve the same basic function and all of which have similar three-dimensional structnres. We have also noted the species specificity of insulins among mammalian species. Here too we find a number of conservative changes in the primary structure of the hormone. Although there are exceptions, as a general rule conservative changes in the primary structnre of proteins are consistent with maintenance of the three-dimensional structures of proteins and the associated biological functions. 

Martin, Y.C., Danaher, E.B., May, C.S., and Weininger, D. MENTHOR, a database system for the storage and retrieval of three-dimensional molecular structures and associated data searchable by sub structural, biologic, physical, or geometric properties./. Comput.-Aided Mol. Des. 1998, 1, 15-29. 

The process through which a linear string of amino acid residues newly synthesized at a ribosome folds into a complex, three-dimensional, biologically active protein structure remains poorly understood. Consider how protein-folding contrasts with RNA-folding. Proteins have 20 distinct monomeric units, RNA only four. The amino acids include aromatic, hydrophobic, cationic, and anionic chemical properties compared to four comparable RNA nucleosides. Moreover, secondary and tertiary structures were fundamentally inter-linked in proteins, but are essentially distinct in RNA molecules. 

M. Meyer, J. Suhnel, Biological significance, occurrence in three-dimensional experimental structures and computational studies, in Computational Chemistry Reviews of Current Trends, ed. by J. Leszczynski (World Scientific Publishing, Singapore, 2003), pp. 161-208... 

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