The Birth of Quantum Biology

Roland Piquepaille writes "Just when you finally have grasped the concept of quantum mechanics, it's time to wake up and to see the arrival of a nascent field named quantum biology. This is the scientific study of biological processes in terms of quantum mechanics and it uses today's high-performance computers to precisely model these processes. And this is what researchers at Rensselaer Polytechnic Institute (RPI) are doing, using powerful computer models to reveal biological mechanisms. Right now, they're working on a "nanoswitch" that might be used for a variety of applications, such as targeted drug delivery to sensors."

Comments

How is this any different?

[dorpus]

Scientists have been building 3-D computer models of organic molecules since at least the 1980s, using the same equations to predict likely reactions. It sounds like plain biochemistry given a new window dressing.

Re:How is this any different?

[wass]

Scientists have been modelling chemical systems within the quantum realm for almost a century now. The problem is that there are very few problems which can be exactly solved. Eg, the hydrogen atom is one of the few solvable ones, but in reality that's only solvable when ignoring all the fine structure corrections (no spin-orbit, relativistic, or spin-spin perturbations). Once you get to the 'difficult' problem of only a mere helium atom, which in its simplest form neglecting fine structure is 'only' two interacting electrons orbiting a nucleus that you model as just a point mass with charge +2e, things get very complicated very quickly. Now imagine modelling something more complicated like a benzen ring, then imagine an actual protein.

This isn't anything new per se, just that the complexity of the modelled systems is getting larger, and due to the numercal estimation processes needed to get anything remotely usable these realms haven't been accessible until lately with the increase of computing power. So where does one draw the line between physics, chemistry, biochemistry, and biology? In these cases, what's being modelled are primarily systems consisting of electrons, neutrons, and protons, interacting with Coulomb force (like-charges repel), spin-orbit interactions, spin-spin interactions, Pauli-exclusion principle, etc. Add more atoms, system gets more complicated, and needs bigger computers.

So it's an age-old problem, using almost age-old numerical techniques, running on new shiny computing clusters

Re:How is this any different?

[wass]

Well, physics is much more than freshman ballistics problems, but you're correct in that the complexity becomes significantly more difficult. Eg, in elementary quantum mechanics one can build a 'Hamiltonian' for any system, and usually you approximate things such as excluding the Coulomb force between every set of electrons, and that neutrons, electrons, and protons act as tiny magnets so they interact that way, and that there are spin-relational effcts, etc. Each of these adds terms to the Hamiltonian, but usually there's a convergence as the correction terms are smaller and smaller and can be neglected. Actually, that's why QED is so easy but QCD gets harder, because secondary and higher interactions in QED have decreasing significance but no so much in QCD where things diverge.

So in some sense you know the basic 'laws' of the universe, and right now we have pretty reasonable understanding of most things, neglecting large scales (dark matter, dark energy) and large energies (Higgs boson, gravitons, etc). But for stuff within our local spheres of observation, we have basic laws that account for most things we can see, so we should theoretically be able to model anything in this frame. The problem is that it becomes super complex very quickly.

Okay, so why there are so few solvable problems is mathematical. Eg, in the hydrogen atom, we can easily solve the differential equation that comes from the Schrodinger equation. Ie, you write the kinetic energy as T=p^2/2m, you write the potential energy as U=-e^2/r, giving a total energy of E=p^2/2m - e^2/r. You should recognize this as the standard kinetic energy written using momentum instead of velocity, and the Coulomb potential energy between the electron and proton. The system is an electron orbiting a proton, and in the center-of-mass units r is the distance between the two, and m is the reduced mass, which is fairly close to the electron. This is all well and good, and when put into the realm of quantum mechanics, r and p go from being canonical coordinates to being canonical operators. When put into the position basis, the p operator acts as a derivative of the r coordinate, and this yields a differential equation that must be solved to give the eigenstates of the solution. The system is spherically-symmetric which makes things much easier, and after solving the three-dimensional 2nd-order differential equations you get the solutions of atomic orbitals that you probably studied about in high-school chemistry class.

Now this is the 'simple' system. When you start adding relativistic corrections to that kinetic energy and when you add the interaction of the electron's magnetic moment interacting with the magnetic field creating as it orbits the proton, this yields the fine structure. You can also add in the spin-spin interaction between the magnetic moment of the electron and the proton, which gives the hyperfine interaction. Each of these things makes the differential equations MUCH harder to solve, and at some point we just don't mathematically know how to solve these complex systems of equations. Helium atom gets much harder because there are now two position coordinates of each atom, and an extra Coulomb interaction term. This is a quantum three-body problem, and even in classical mechanics the three-body problem cannot be solved in general. Ie, there is no KNOWN exact solution for any three bodies.

Anyway, you can see where this is going. But while we cannot know exact solutions, we can approximate them numerically to arbitrarily-small precision (at least with classical mechanics where there is no uncertainty principle). This is where the shiny computers come in. We can model easily how 10 bodies orbit around the sun AND interact with each other, but to get a general algebraic solution of them for any point in time, we cannot do.

Uncertainty principle and medicine

[Anonymous Coward]

So, when I am seriously ill and get quantum biology based medication, will I be in a superposition state of 'getting better' and 'dead'?

Doesn't work

[Intron]

I tried firing hundreds of cats through two narrow slits and I didn't get interference patterns.

Re:Doesn't work

[spun]

Check your data and methodology. I've found that when the distance seperating the two slits is less than one cat-length, a single cat fired at the slits can interfere with itself, as evidenced by the distinctive banding in the blood spatters. Of course, if the slits are further than one cat-length apart, no interference patterns appear. Then all you get is a cat-ass-trophy.

Puhleease: Put Roland Piquepaille blog elsewhere

[viking80]

would like to just suggest a link to Roland Piquepailles blog somewhere where those who are interested can click. And *no more articles please*

I read /. to get real news and facts, and see discussions from people with insight.
Roland Piquepailles submissions has not met this criterium. At least filter away the combination "Piquepailles", "nano" and "quantum".

Take a bottle of nano-beer (yes the water molecules are nano particles), eat some nano-pretzels (the baking soda produced a nano-gas that puffed them up), and run this script.

Here is one of many greasemonkey script to remove piquepaille stories
http://userscripts.org/scripts/show/5735/

You should mod this up if you agree or mod away as flamebait/offtopic/troll if you dont agree, but at least mod it.

Re:Did someone say Quantum Biology?

[metlin]

Same-sex appeal? I didn't know quantum physicists were mostly gay...

Oh, they are just not sure - nobody's opened the closet yet to find out. =)

Re:HOW IS THIS A TROLL??

[exp(pi*sqrt(163))]

I think many people really don't appreciate how difficult quantum simulations are. I was pretty surprised when I worked in pharmaceuticals for a bit and saw how much CPU time was being expended on fundamentally simple ball-and-stick simulations. (Ball-and-stick seemed to be standard terminology, even though it looks like a derogatory term.) I was also pretty shocked by how many tunable parameters there were - mainly because things like bonds were added ad hoc rather than emerging naturally from the simulation. Bonding is fundamentally a quantum phenomenon so it can never emerge from a classical simulation without being explicitly added as a kind of spring. And because bonding doesn't really make sense in a classical context, it actually behaves very differently from any kind of spring, and that's why you have to keep tuning the spring parameters to make things look reasonable.

But when I realised how hard quantum simulations could be it started seeming reasonable again. Quantum simulations aren't just an order of magnitude more difficult. The order of magnitude of difficulty can itself be an order of magnitude bigger!