By selectively unlocking the IFE “lock” with different DNA “keys”, diverse basic, advanced and concatenated logic circuits, a logic-controlled molecular RGB-signal-light, triple-parallel-arrays are successfully constructed.
All of the above logic operations demonstrate the strengthened reliability and practicality, powerful integration capability and improved computing complexity of this UCL logic library.
Assuming one was trying to solve the problem on a computer working at 1 trillion operations per second, this computation would take 10135 seconds - vastly longer than the age of the universe!
"I didn't want to do a cheap pet trick," says Adleman of choosing this problem.
Answers can only be found by crunching through every possible solution, and most hard problems are too difficult for humans or computers to solve.
Finding a Hamiltonian path connecting 100 cities using a well-known algorithm, for example, would take 10147 operations.But what message should be encoded there if DNA was going to solve a computational problem?After six months of intense research, scribbling out formulas, often reduced to an agitated trance, Adleman shouted Eureka!Using what is essentially a four-letter alphabet, DNA stores information that is manipulated by living organisms in almost exactly the same way computers work their way through strings of 1s and 0s. If the answer's yes, new ways of building entirely different kinds of computers would open up - computers so fast they could solve some of today's unsolvable problems, so small they would exist at the molecular level.Thanks to learning algorithms and other evolutionary tools being incorporated into computers, the machines around us are becoming more lifelike.DNA computing has shown impressive developments and exhibited amazing power over the past few decades.However, most current DNA logic devices can only produce single-modal output that is monochromic or even invisible, which greatly limits their reliability and practicality, integration capability and computing complexity.It was Christmas of 1993, and two unexpected gifts lay in front of him: a design for the world's first molecular computer, and its first problem to solve.Adleman imagined testing his DNA computer with something called a directed Hamiltonian path problem.(The Hamiltonian path was named after Irish mathematician William Rowan Hamilton, who devised the routing conundrum in 1857.) A simplified version of this, known as the traveling salesman problem, poses the following question: Given an arbitrary collection of cities a salesman has to travel between, what is the shortest route linking those cities?Adleman's version limited the number of connecting routes between cities by specifying in which cities the salesman should begin and end his journey.