Structural View of Biology
The major molecules of protein synthesis, from DNA to RNA to ribosomes to folded proteins, are available in the PDB archive. Proteins are built in several steps in all living organisms. The blueprint for each protein is stored in the genome, encoded in strands of DNA. This information is transcribed into an RNA copy, which is then used to construct the protein chain. After the chain is synthesized, it may be modified with special chemical groups, chaperoned into its proper folded shape, and ultimately destroyed when it is not needed any longer.
Structure of Nucleic Acids
Nucleic acids carry genetic information in the sequence of nucleotides. Two forms are commonly found in cells: DNA is the primary storehouse of genetic information, and RNA is used in many information-carrying and catalytic roles. DNA is commonly found in a double helix of two complementary strands, and RNA typically forms complicated folded structures.
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Each of the cells in your body carries about 1.5 gigabytes of genetic information, an amount of information that would fill two CD ROMs or a small hard disk drive. Surprisingly, when placed in an appropriate egg cell, this amount of information is enough to build an entire living, breathing, thinking human being. Through the efforts of the international human genome sequencing projects, you can now read this information. Along with most of the biological research community, you can marvel at the complexity of this information and try to understand what it means. At the same time, you can wonder at the simplicity of this information when compared to the intricacy of the human body.
DNA is a perfect raw material for constructing nanoscale structures. Since base-pairing has been selected by evolution to be highly specific, it is easy to design sequences that will link up with their proper mates. In this way, we can treat small pieces of DNA like Tinkertoys, designing individual components and then allowing them to assemble when we put them together. In addition, the chemistry of DNA synthesis has been completely automated, so custom pieces of DNA can be easily constructed, or even ordered from commercial biotech companies. This puts DNA nanotechnology in the hands of any modest laboratory, and many laboratories have taken advantage of this, creating nanoscale scaffolds, tweezers, polyhedra, computers, and even tiny illustrations composed entirely of DNA.
Since the process of DNA-directed protein synthesis was discovered, scientists and philosophers have searched, more or less seriously, for a relationship between the triplet nucleic acid codons and the chemical nature of the amino acids. These attempts have been uniformly unsuccessful, but remain an occasional topic of speculation because of their possible insights into the origins of life. There does not appear to be a specific interaction between the codons and the amino acids themselves. Instead, the match is made by transfer RNA, the Rosetta Stone that translates the nucleotide language of codons into the amino acid language of proteins. This translation is physical and direct: at one end of each tRNA is an anticodon that recognizes the genetic code, and at the other end is the appropriate amino acid for that code.
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