Hacker News Reader

Comment by dekhn | Hacker News Reader

I'm not sure I've seen reliable examples other than photosynthesis, and it hasn't been "a long time". Happy to inspect your sources.

View on HN

Depends on what you mean by reliable examples, but it's been researched for well over 25 years. And point where something goes from probably to clear cut gets fuzzy.

(2009) "Quantum biology? Tunneling in enzymes" Over the past two decades the possibility of quantum tunneling of protons in enzymes has attracted considerable attention. (See for example a piece in Nature by Philip Ball (my favourite science writer) or the proceedings of a meeting at the Royal Society

The observed large kinetic isotope effects and their temperature dependence are inconsistent with semi-classical transition state theory,

http://condensedconcepts.blogspot.com/2009/07/quantum-biolog...

PS: This post ended with I align myself with the skeptics, but it's hardly a new idea.

That work is highly speculative (I've studied, but not as my primary work, enzyme kinetics and reaction mechanisms). Finding holes in transition state theory isn't hard and I don't see that it's necessary to invoke tunneling protons to come up with better theories. Even the physical experiments cited in the Ball article, are pretty speculative, and aren't accepted by the mainstream.

I find it pretty amusing, because I proposed tunneling protons in a journal club once, but got laughed down by all the physicists who said "that's silly, proton mass is too high, so probability of proton tunneling is basically zero" (they were being overconfident).

The only real work in this area, which is to say, work that is heavily backed up with data, is the work on quantum mechanisms in photosynthesis: http://newscenter.lbl.gov/2010/05/10/untangling-quantum-enta... This work, since it has a huge amount of high quality experimental work, is considered pretty solid.

Interesting, I have heard it suggested that tunneling is one of those things that's clearly going on, but not necessarily relevant. Much like how relativity is required for sufficiently accurate solar system models, but you can generally ignore it.

That's possible, but where is the evidence to show it? I'm not saying tunnelling isn't occuring (the laws of physics permit it) but if it's not relevant, who cares?

And i had a committee member forbid me from including quantum effects in the modeling of my enzyme. He said it was "too speculative". All science is speculative, until it isn't. You would be well served to reduce your "highly speculative" filters. That is, continue to propose your interesting new chains of causation. If there were braver people than me (which shouldn't be hard) then perhaps understanding enzyme mechanisms would be further along by now.

People need to back up their speculations with evidence.

Also, did you push back against the committee member? Show data? At least create a plausible doubt in their mind?

The reason enzyme mechanisms are so hard to study is that getting proteins into a state where you can capture data from that femtosecond where the reaction occurs is hard. Recent improvements in free electron lasers for fourth generation synchrotrons will greatly improve this.

Roger Scrunton, Manchester Uni, Quantum Effects in Biological Catalysis

https://www.youtube.com/watch?v=SnxmHlbtJDI

The ammonia maser uses proton tunnelling.. the guy who invented that also got "laughed out of the room". Well, it's probably a different pressure / temperature than enzyme kinetics, but those physicists, they like to own the quantum and not let anyone else have it. :-)

When I studied undergraduate quantum mechanics (physics dept, many years ago) one of our homework problems involved oscillation of the ammonia atom. Ie, the three hydrogen atoms form a triangle, and the nitrogen atom is in a superposition of states above or below the hydrogen plane.

Iirc, given some estimate of the relative potential energy barrier formed by the hydrogen atoms, we showed that the nitrogen atom would effectively oscillate between the up and down states and calculated the frequency of oscillation.

I've been hearing quantum superposition and tunneling as a factor in enzyme mechanisms at least since I was a grad student (circa 1988ish). It was all the rage that perhaps it was the main enzymatic mechanism; but, it grew a little less popular as more 'conventional' explanations seemed to provide acceptable kinetic models. "sources"? too many to list, but just search for quantum effects and enzymes and set your last date to something like 1990ish, like here: https://scholar.google.com/scholar?q=enzyme+mechanism+quantu...

Yes, I think the work that was published in this area was mostly speculative. I want links to mainstream stuff that I can put a little more trust in, like the work done at LBL on photosynthesis and entanglement.

Just look at some of those names in the authorship of that haphazard search link i included. Richards, Pullman, McElroy, Bhattacharyya, Pauling ... If you can't put trust in some of those folks then you won't find it in general. (whatever the hell "trust" has to do with good science, notwithstanding)

Pauling was a genius, great contributions to chemistry, but he also thought vitamin C was the cure for everything. I'm a "real scientist" and I can judge evidence for myself.\

Random searches on terms bring up a lot of stuff, but it takes time to evaluate everything. On the other hand, I'm already up to speed on the state of the art in protein chemistry, and I'm not seeing strong physical evidence from experimentalists supporting this.

Judith Klinman's work at Berkeley includes proton tunneling in proteins.

http://www.cchem.berkeley.edu/jukgrp/klinman_group/Research....

more accurately, they study proteins and use proton tunnelling as a possible mechanism for their function. But I don't think their work is universally accepted.

Reply on news.ycombinator.com