Viswanathan K's Thoughts

As I wrote earlier , Bragg had found a way to know the structure of a crystal. But as Venki Ramakrishnan writes in Gene Machine , Bragg’s method involved making guesses about the structure that would explain the observed pattern of concentration spots. This was not a practical approach as the number of types of atoms in a molecule increased.   Perhaps you are wondering: “Couldn’t we just use X-rays with a lens to see images of molecules directly?” Aha, writes Ramakrishnan, that’s not an option because: There is no lens that’s capable of making images of molecules based on X-rays; Worse, X-rays have a lot of energy, so they “damage the molecules they hit”. In other words, they end up distorting the very thing they observe.   Well, ok, can’t we solve Issue #1 above (no lens problem) by having a computer do the maths that a lens, had it existed, would have “done” to create the image? Not really, says Ramakrishnan, because a real lens combines both the amplitude and...

In his book, Gene Machine , Venki Ramakrishnan explains how we “see” molecules and DNA strands. Actually, that’s not entirely true. Here’s why: “When light passes through a very narrow opening or around the edge of an object, it spreads out… in a process called diffraction… If two very small objects are close together, their images spread out and merge with each other.” This puts a limit on resolution capabilities of any viewing instrument: “Someone looking through a microscope would see just one large fuzzy object rather than two distinct ones.”   Ernst Abbe calculated that you could see two objects as separate if they were no closer than half the wavelength of the light used to look at them. Therefore, no matter what the magnification power of the microscope, one can’t see anything smaller than half the wavelength used to see, i.e., ½ of 500 nanometers (a nanometer is a billionth of a meter). And since molecules are smaller than that: “It would be impossible to see in...