- Nov 12, 2008
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Science!
This is very exciting to here, but it shouldn't be all that terribly surprising. This is going to over-simplify things a tad, but it still explains things well. Arsenic(As) is isoelectronic with phosphorus(P). What this means is, that the atom itself behaves in a similar pattern to that of phosphorus. There are differences, however the difference between nitrogen and phosphorus (which are also isoelectronic), but the difference between phosphorus and arsenic, is much less pronounced. The reason it is far more pronounced in N vs. P is nitrogen does not have d-orbitals (a type of electronic state), where P does. As and P both have d-orbitals, As simply as more of them. However the difference between individual d-orbitals is much smaller then p-orbitals (a lower level orbital) that is more often involved with bonding. Because the differences between P and As are much smaller, it makes sense that you could substitute one for the other on basic structures such as DNA. As in general is weaker and more diverse in bonding then P is. It does have a bit more metallic character though, so that in turn would also impart some limitations.
It shouldn't be all that surprising that this can occur because of the strong similarties between P and As. The reason we have not seen it until now though, is because in order for As to be "safe" for an organism, As must be an intergral part of its biology. As is toxic in organisms because of it's similarity to P. It is able to be absorbed biologically, intergrated, bond, and interact. However there are small enough electronic (and in some cases, steric) differences that proteins can't recognize it, or they aren't equiped to bind or unbind the As compounds. With these new organisms though, As is intergral to its biology so it is actually needed. It's highly like that all of its proteins and cell systems are designed exactly for As compounds. This in turns could mean that high levels of phosphorus compounds are toxic to this organism.
One can easily make a leap of logic and intution to say that this strongly diversifies the possibillites of "life" throughout the universe, and indeed it does. However, I personally feel that this form of new life is likely limited to primitive organisms. Why? Because these heaiver/larger elements are not as common. While present, they arent persistent in common compounds nearly as often as elements like C, P, S, and O. There is less material to work with so it will be more difficult to uptake and intergrate. Further the idea of Si based organisms is novel and interesting to think of, the problem is Si based systems tend to form crystal lattices, not discreet molecules like carbon. Si based organisms are likely possible, but the sheer amount of fixes and needs for such a creature likely completely subvert all the expectations of common biology. I have reason to believe it would have something vastly different from DNA, likely baring no resembelance to it what so ever.
Definitely exciting news, on the basic level not too surprising, and definitely lends to how we might have to define "life" in the future.
This is very exciting to here, but it shouldn't be all that terribly surprising. This is going to over-simplify things a tad, but it still explains things well. Arsenic(As) is isoelectronic with phosphorus(P). What this means is, that the atom itself behaves in a similar pattern to that of phosphorus. There are differences, however the difference between nitrogen and phosphorus (which are also isoelectronic), but the difference between phosphorus and arsenic, is much less pronounced. The reason it is far more pronounced in N vs. P is nitrogen does not have d-orbitals (a type of electronic state), where P does. As and P both have d-orbitals, As simply as more of them. However the difference between individual d-orbitals is much smaller then p-orbitals (a lower level orbital) that is more often involved with bonding. Because the differences between P and As are much smaller, it makes sense that you could substitute one for the other on basic structures such as DNA. As in general is weaker and more diverse in bonding then P is. It does have a bit more metallic character though, so that in turn would also impart some limitations.
It shouldn't be all that surprising that this can occur because of the strong similarties between P and As. The reason we have not seen it until now though, is because in order for As to be "safe" for an organism, As must be an intergral part of its biology. As is toxic in organisms because of it's similarity to P. It is able to be absorbed biologically, intergrated, bond, and interact. However there are small enough electronic (and in some cases, steric) differences that proteins can't recognize it, or they aren't equiped to bind or unbind the As compounds. With these new organisms though, As is intergral to its biology so it is actually needed. It's highly like that all of its proteins and cell systems are designed exactly for As compounds. This in turns could mean that high levels of phosphorus compounds are toxic to this organism.
One can easily make a leap of logic and intution to say that this strongly diversifies the possibillites of "life" throughout the universe, and indeed it does. However, I personally feel that this form of new life is likely limited to primitive organisms. Why? Because these heaiver/larger elements are not as common. While present, they arent persistent in common compounds nearly as often as elements like C, P, S, and O. There is less material to work with so it will be more difficult to uptake and intergrate. Further the idea of Si based organisms is novel and interesting to think of, the problem is Si based systems tend to form crystal lattices, not discreet molecules like carbon. Si based organisms are likely possible, but the sheer amount of fixes and needs for such a creature likely completely subvert all the expectations of common biology. I have reason to believe it would have something vastly different from DNA, likely baring no resembelance to it what so ever.
Definitely exciting news, on the basic level not too surprising, and definitely lends to how we might have to define "life" in the future.
