Life minus Nine

We define life in many ways. All the research in the world is aimed primarily at only one target - improving human lives. The past steps lead us to a new gate called ‘nanotechnology'. Although research in this field has been going on for decades, it is only now that the focus light is turned on. It will be worthwhile to spend some time on it.

Nanotechnology, like life, can be defined in many ways, its areas extending far beyond just physics, chemistry, or biology. Here, I try to relate these hard-to-define terms, "life" and "nano". What would life be 'minus nine'? I would rather prefer to talk about life 'plus' nine.

It is customary to define nanoparticles or nanostructures as entities in the range of sizes from 1 - 100 nm, thus many biological materials can be classified as nanoparticles. Considering a gradation in this range, we can include, viruses, which range in size between 10 to 200 nm, in the upper part of the nanoparticle range. Proteins, ranging between 4 and 50 nm, are in the low nanometer range, while the building blocks of proteins, the amino acids - each about 0.6 nm in size - are below the lower limit of a nanoparticle. These are a few of the examples that could be considered in the nanoscale. The structures made up by these particles sometimes end up in the same range too.

A protein is a combination of any of the 20 amino acids, bound together one after the other by strong peptide chemical bonds. These chains called polypeptides contain hundreds, and in some cases thousands of amino acids; hence they correspond to "nanowires". The polypeptide nanowires further undergo twistings and turnings to compact themselves into a relatively small volume forming a polypeptide nanoparticle, with a diameter that is typically in the range of 4 - 50 nm. Thus a protein is a nanoparticle consisting of a compacted polypeptide nanowire.

The genetic material deoxyribonucleic acid (DNA) has the structure of a compacted nanowire. It is made up of 4 nucleotide molecules that bind together in a long double helix to form chromosomes. Thus the DNA molecule is a double-nanowire, with the strands twisted around each other with a repeat unit every 3.4 nm, and a diameter of 2 nm.

Another biological structure made up of subunits in the nanometer range size is the human tendon. The function of a tendon is to attach a muscle to a bone. The fundamental building block of a tendon is the assemblage of amino acids that form a gelatin- like protein called 'collagen' (1 nm), which coils into a triple helix (2 nm). Further arrangement then follows a three-fold sequence of fibrillar nanostructures: a microfibril (3 - 5 nm), a subfibril (10 - 20 nm), and a fibril itself (50 - 500 nm). These nanostructures then make up the macroscopic tendon.

A view of these biological nanostructures would give us an idea what role the study of nanoparticles plays in biology. Taken to the scrap, many important biomolecules may end up in nanoparticles. Since the smallest amino acid, glycine is 0.42 nm in size, and some viruses reach 200 nm, it will be appropriate to define a biological nanostructure as being in the nominal range from 0.5 to 200 nm. It is our discretion to study them as a separate class, to place them in a separate group, or to create a new field called 'nanobiotechnology'.

Remember, best things come in small packages!