 What is co-operativity? Lot of slides are there it is written form I will explain very briefly first here. The moment one of the oxygen binds like this, how it binds? It binds like this iron porphyrinside, iron sorry iron porphyrinside this is imidazole that is the deoxy hemoglobin no oxygen is there. This is the other histidine that I am talking over here which is for this is the reduced form oxygen binds with it and what happens this is the oxy form oxy hemoglobin and there is a hydrogen bonding ok. Now, the moment it binds this is definitely going to come one from the other in the exam what happens? This iron in the deoxy form is in reduced form ok both the structure we are discussing only iron 2 plus no iron 3 plus iron 2 plus iron 2 plus see this is not a very good ligand it is too far it is not going to bind you have a porphyrin ring and a imidazole. This is iron 2 plus high spin it is a high spin configuration and this iron is not really in the plane. So, if the porphyrin plane is here iron is sitting half in half out it is not into that cavity perfectly. So, as you can see you can see the iron on top it is of course, little bit in the cavity, but it is on the little top ok it is not really inside the porphyrin cavity. What is the porphyrin cavity we were saying showing here this is the cavity right. Now this is iron 2 plus in high spin form the moment oxygen binds ok the moment oxygen binds over here it goes to low spin form. So, it is now a octahedral complex perfect or not perfect it is a very good octahedral complex right and you know that iron 2 plus high spin means what D 4 sorry T 2 G 4 E G 2 upon the oxygen binding it goes to T 2 G 6 E G 0, T 2 G 4 E G 2 this is T 2 G 6 high spin to low spin configuration change the moment high spin to low spin configuration change is there. So, there is T 2 G E G all of a sudden there is no electron in E G and therefore, what happens is the repulsion of the ligand becomes less and the size of the iron decreases. So, in this case iron 2 high spin is larger in size low spin is little bit shorter inside little bit shorter that is good enough that means, it will go into the cavity in the porphyrin and thereby then that that pull that is a structural change. So, this immediately you can see it was bind or it is bind with the iron center and it is like big iron center is big the moment it gets certain it just so, it is over here iron is here it is make it little shorter and then it pull in that change it is over here it goes down that change that change will trigger the cooperativity what will happen the moment it gets pulled in the cavity that change in configuration or confirmation will be relayed all over that will send the message the moment one oxygen binds in here it pulls in or it passes the information and this guy knows that oxygen is available and it almost again this guy undergoes high spin to low spin configuration change oxygen comes and sit down it happens to here it pulls in again it relayed it relayed. So, the activation barrier or how much energy you need to put for the first oxygen is always going to be high the moment you are able to bind the first oxygen second third fourth is going to be less less and less it is it is just a relay I mean you are having a 1600 meter race let us say it is it is just gets relayed very first if there is a message that oxygen is there the high spin to low spin change is happening oxygen binds oxygen binds high spin iron 2 plus goes to low spin iron 2 plus it gets reduced in size it gets pulled in the pocket of porphyrin that little change it is a very subtle change it gets communicated with the next porphyrin center that next porphyrin center binds oxygen it gets communicated next one it gets communicated next one. So, the that is cooperativity they are cooperating they are you know working in tandem they are very good communicator they are communicating with each other ok. Now, that is cooperativity it is very nicely also written in the slide form I will come I may not discuss way too much afterwards ok. Now, so how the binding happening this is oxygen these are let us say these are oxygen 2 electrons it is metal sorry ligand to metal bonding is happening ok. It gives to the d z 2 orbital the axial position right it give to d z 2 and from d z x orbital it donates back to the oxygen pi star orbital right. So, it is a back bonding it is forward bonding and then back bonding that means that the binding is going to be good it is of course you know it is not too tight, but it is good iron center will bind with the oxygen decent amount that is that is occupied means field one will be donating and then there will be back donation ok will not get into too much details of that. Now, this is what exactly this is what exactly I tried to say I will just briefly go through the slides it will be provided to you in the model. So, I will be going directly now iron 2 plus this is high spin paramagnetic of course it is high spin paramagnetic right because it is T 2 G 4 E G 2 high spin right iron 2 plus paramagnetic T 2 G 4 E G 2 the moment oxygen binds it becomes low spin diamagnetic T 2 G 6 E G 0 no unpaired electron yeah. Now, it is not really octahedral, but it is you know it, but still there is a loose coordination as I was showing this heistedine is there the moment it is there it is of course the sixth coordination side is almost vacant it is not 100 percent vacant almost vacant ok. Now, of course, you can see that this information iron 2 plus 2 this iron 2 plus I mean not really deoxy hemoglobin to oxy hemoglobin changes this will also have some effect in the spectroscopic behavior ok. What we are not discussing here is right after oxygen binding iron oxidation state also changes iron 2 2 2 goes to iron 3 plus oxygen becomes superoxo reduced by 1 electron that we are not discussing you do not have to write in the exam do not write in the exam. Oxygen gets reduced by 1 electron that is called superoxo what we have discussed here is paroxo and iron 2 plus gets oxidized to iron 3 plus that is a reversible process means it can go forward and then come backward as well anyway. Now, this due to these all these changes will get a spectroscopic difference the color or if you if you measure before oxygen binding and after oxygen binding the spectra of the compound will be different based on that we can measure how much oxygen is bound let us say some people you know suffer from you know this less oxygen delivery to certain part of body that is bad right. So, maybe enough for firing center are not there ok. So, how much let us say at a certain body part how much oxygen is there that you can calculate it is a very simple test you take the blood or you take some site specific reaction or site specific study a specific area you just see or in general you can figure out how much is there. So, how much oxygen content is there from this spectroscopic change you can find out that is what you know pulse oximeter is ok you can just read and understand nothing in there. Now, what happens when oxygen binds to hemoglobin I think I have discussed already. So, high spin goes to low spin all the information is covered. So, this phenomenon is called cooperativity for your exam purpose these are the slides the exactly same thing what I have said without looking at these slide that those information are there you read it ok. Now, see there are some slides I will take 5 to 10 minutes to discuss this is for your general understanding all the problem is the let me in 1 minute let me discuss the problem. So, all other section whoever are that you know instructor they have discussed it ok. So, I have to discuss it ok simple, but I will give this slide in this form. So, you decide how much you want to read how much you do not want to read I have given it is for your information I am very clearly saying I think we are not going to I mean most likely 90 percent guarantee may be some information understanding may be tested, but not in deeper level ok. Let me get into that you will see it is not that boring all right. All let me go to the next slide it is interesting right we do know that our blood is red. Then there are some animals some other species which who had blue blood. These are not demons not in movies those blue blooded there are cold blooded people, but these are blue blooded animals ok. So, the reason why I this is again not for example, I mean give me 5 minutes I will finish it it is important that you understand never you are going to look back perhaps ever again these things ok. It is important you just do understand little bit. I will discuss some little bit interesting thing ok including Daru ok how it get digested ok. So, in our blood we have we have these porphyrin center right iron center these other cases we in lot of other animals or some some of these you know these marine invertebrates they do not have the blood or so called blood as we see in red because they have of course, they have to take oxygen I mean all we are saying is these are the oxygen carrier protein. The way they carry the oxygen is little bit different instead of iron center there you have copper centers those or these porphyrin iron center instead of those you have copper centers that gives it blue color. So, there are some of these haemocyanin or some of the animals are there some of the species are there which have blue blood right. At the end of this class we will be discussing tutorial part. These are the one where we have again slide will be given I think I may not be allowed too much, but it is ok. So, there you will be saying the blue blood ok there you will be saying the seeing the violet ok violet pink color due to the fact that the ligand is different or the metal is different or both is different ok. Therefore, although oxygen binds mode of binding is different ok. Now, these are the slide amino acid peptides and protein you know it amino acids is something like this acid and the amine part amino acid put together is protein backbone right. And these are different amino acid we are talking aspartic acid glutamic acid lysine serine cysteine lot of I am not asking you to memorize, but if I think 3, 4 amino acid you must know this is your responsibility if someone is asking question I cannot help ok. So, few amino acid you must know and you know the that is how the peptide backbone is formed and then those peptide backbone can have the hydrogen bonding or interlinked or crosslink and thereby they can form the you know 3D structure ok. That is I think you have started in biology or somewhere or you just essentially understand how it forms fine. Next is enzyme substrate complex I will take you here. Enzyme substrate complex is what? You have a organic compound organic you have taken you see lot of carbon hydrogen bonds are there and if that organic compound is getting functionalized let us say hydroxylated lot of possibilities are there right only a particular carbon hydrogen bond gets functionalized. How does that happen? That happens because let us say you have a porphyrin center or a iron center in front of that whole organic molecule is there it is not like that only a particular carbon hydrogen bond gets exposed or comes very close to the active site that metal active site metal Ongi and therefore, even if you have all those carbon hydrogen bond or carbon hydrogen bond covalent bond present all those hydroxylation products are possible only selectively one carbon hydrogen bond gets functionalized because that is how it gets exposed not these are getting functionalized only let us say this is getting functionalized hydroxylated you see only one particular C H is getting hydroxylated. Now that is called substrate binding pocket substrate comes in there is metal binding pocket there is substrate binding pocket substrate comes in and sits in there and the metal is there and the chemistry happens ok. Now show enzyme and substrate interaction those E S complex we are saying this is where you know the substrate is bound by relatively weak forces substrate is not going to bind bound that organic substrate let us say is not going to be bound very strongly they forms weak complexes ok. Another important thing is to understand enzyme is huge not everywhere it is binding substrate there is only a specific center where it binds right. Now rest of the things may not be involve in catalysis this is the reaction we are trying to tell it is catalysis right it is a reaction happening rest of the protein backbone or peptide backbone we are not seeing much of a role in the substrate binding only a particular site or particular place substrate comes in sits in there and the enzyme or let us say metalloenzyme does the chemistry the or the catalysis part. So, something about the enzyme substrate complex is given in the slide it is a very easy to understand I am once again I do not expect you to memorize all these you know these things these are not of much of use for the course purpose, but you try to flip through give yourself 10, 15, 20 minutes some idea wise if some question is coming you should not be complaining. We are not going to ask you to draw peptide bond ok right anyway. Now let us move on this is one of the thing I was trying to tell you synthetically see if this is the umbrella like structure you see the umbrella is forming over here ok. Now, oxygen is prevented in the synthetic system oxygen is that is how prevented from reacting at the other center that is that is you know that is just a view you see that how people make the porphyrin functionalized porphyrin from porphyrin backbone how people put the umbrella and put the oxygen in a protected manner it is protecting whoever is not interested please be my guest leave it ok or do not be my guest. Now, carbonic anhydride there are certain enzyme this is called one of the enzyme called carbonic anhydride that has zinc site at the middle. Now it is coordinated with histidine, histidine, histidine and water what it does it converts carbon dioxide into carbonate ok. How it does again you do not have to memorize you just see one time it is a very easy organic chemistry I am talking about. You have zinc hydroxo formation zinc water to zinc water was there ok and three histidine was there these are the ligand for zinc 2 plus zinc is redox inactive zinc 2 plus stage zinc 2 plus water gets deprotonated water itself deprotonation will not be easy, but the moment it binds with this Lewis acid zinc 2 plus acts as a Lewis acid the acidity it becomes highly acidic this OH bond deprotonation become easier water itself under the physiological condition it will not let us say undergo deprotonation. Now the moment water binds with the zinc 2 plus zinc 2 plus is a Lewis acid and thereby you will have an opportunity to deprotonate the moment the hydroxy forms carbon dioxide can be attacked by this hydroxy and then you can form the carbonate. So, sodium bicarbonate it is something like that. So, carbon dioxide forming carbon bicarbonate or carbonate ok. So, that is the carbonic anhydrase activity it carbon dioxide reacts with water it is a simple reaction, but it is not that very easy at all I mean you take carbon dioxide gas put water how can you react, but simple zinc side can do the wonder it is catalysis very very good and these are all happening in our body when come on it is very important ok. Now, then this peptide back bond cleavage of course, you know how to cleave a amide peptide bond it is an amide linkage right hydrolysis you need to do, but these hydrolysis in organic chemistry what you learn it may not be efficient may not be fast ok it is slow enough, but the moment you have this zinc side this cleavage becomes easy ok it is it cleaves actually in a similar manner. So, this hydroxo this zinc hydroxo that forms over there this zinc hydroxo attack over there of course, let us say base catalyzed hydrolysis of amide is possible it is a amide bond is there you put a base a nucleophile attack at that center and it gives you an acid part from here and amine from here right it is a hydrolysis ester hydrolysis you have studied it is a amide hydrolysis, but that amide hydrolysis is very slow under you know physiological condition, but the moment zinc side is there zinc hydroxo forms due to zinc being the Lewis acid deprotonation becomes easier deprotonation of water becomes easier that zinc hydroxy can do this wonder ok. If you drink if you drink alcohol your liver will be damaged why it is very simple reason right your liver is going to be damaged that is mainly all first to remind you ethanol is the one which is used as alcohol to drink not the methanol the methanol you drink again I will see you ok alright. So, why ethanol and then how our body digest it or breaks it it is not good for our body it is a foreign object we get high, but that is why we drink ok, but all not necessary I do not promote just like movies any actor does not promote any of these these these I do not promote anything I am not promoting anything and that is a very serious note it is an academic institution ok. Now, now so how although definitely people drink alcohol that is a fact how body digested what happens alcohol ethanol CH 3 CH 2 OH ethanol is converted to acetaldehyde CH 3 CH O alcohol oxidation to aldehyde happens and then aldehyde gets chopped off to carbon dioxide and water and so on that is another enzyme the first step ethanol to aldehyde formation that happens in here the enzyme called lead liver alcohol dehydrogenase it is nothing, but once again it is a zinc enzyme ok. Alcohol if that is why liver gets damaged if the enzyme is not working which is at the liver that enzyme is not working of course, our body will not have the ability to dispel carbon I mean dispel the alcohol from our body right. If liver alcohol dehydrogenase is not working that enzyme is not working alcohol becomes toxic for us I mean of course, it is toxic, but it becomes even more toxic right it is it could be deadly I mean if someone has it is deadly yeah you do see the news someone has liver which is damaged and keep on consuming alcohol of course, right. So, this is how it happened it is a little bit different mechanism I will not you do not have to remember again what happens over here is this is the pyridine ring you are seeing it is called nicotine or something like similar moiety is there in your cigarette also nicotine ok I will find let us stop there. So, this hydride so, zinc center binds with the alcohol R in CH 3 methyl CH 2 OH now gets deprotonated and this hydride gets transferred to this pyridine ring it is a this is the this is the center which is helping and the enzyme is zinc enzyme ok zinc center with three of them zinc center with all those coordination the alcohol bind in here and the way alcohol is converted to aldehyde is shown is there it is a hydride transfer mechanism simple organic reaction, but without this enzyme you can understand this process will not happen and it does not happen that is also true for lot of lot of these you know East Asian people like Chinese people Korean people you see the moment they drink alcohol their whole body goes red not all of them some of them fortunately for us we are most of us are a lot of us are not most of lot of us are brown. So, we do not show up that much all Chinese lot of Chinese people lot of Korean people South Korean people as far as at least I have seen actually they do not have this enzyme sufficient amount of course, how your you know it goes back to your gene it goes back to your evolution or the you know your generation how it has come see you know that is that is how if the enzyme is not there in enough quantity what will happen is they are not able to digest or take much amount of alcohol little bit is good enough for them their you know body gets you know swollen or red color it is just like almost like a allergic symptom it showed up of course, some of us can have the exactly same symptom if your body or if your liver is not having this enzyme anyway enough for that. So, this is some information about the cis platin how much money you can make you can be a trillion year a billion year dollars not rupees you can you can be of course, rupees is good enough you can be if you have discovered a good drug if you have discovered a good catalytic reaction simple thing I did not discuss let us say water to hydrogen production that is another enzyme since the class is only one we did not discuss that there is an enzyme which can convert water to hydrogen right water splitting. Now, if you happen to have a good catalyst for that you know this is fuel right fuel lots of fuel let us say if you have an enzyme there is enzyme if you can convert let us say methane to methanol that is a trillion dollar project if you have a good catalyst enzyme does this thing routinely enzyme is very good at doing this methane to methanol I am giving you target you pick up B bill trillion year give me some money back these are these are ideas methane to methanol you produce hydrogen this lot of simple reaction which nature does it could be in our body it could be somewhere else if you can do develop a good system catalytic system for them I mean nothing can stop you from being rich it has to be efficient it has to be industrially viable industry has to buy your technique chemistry can be rewarding too alright tutorial tutorial what are storage and transport protein we have discussed storage protein storage thing transport proteins transports things the answer is given over here answer is given here if you give me an opportunity I will I will wait for you why cyanide is toxic we have discussed again the binding site over here for oxygen will be occupied by cyanide and thereby it is toxic and you cannot that is an irreversible process you cannot change it ok. So, what is the role of globular protein in oxygen transport it is nothing it prevents the dimerization it prevents oxygen you know iron center to get further oxidized and other side reaction it prevents ok lot of side reaction can happen that can be prevented by this globular protein what is cooperativity everybody knows by now right if you did not understand go through this step wise ok it is fine now why are all the oxygen carriers that contain iron and porphyrins found inside the cell why inside the cell outside the cell is very oxidative atmosphere iron can be oxidized irreversibly to iron 3 plus then you cannot have them used for oxygen carrier right why is the size of high spin iron 2 plus is larger than low spin iron 2 we say that high spin to low spin T 2 G 4 E G 2 to low spin you are going to T 2 G 6 E G is out E G out means lot of repulsion is out and the cell is becoming smaller or sorry not say iron center is becoming smaller high spin to low spin size varies size gets smaller it is written over there what prevents synthetic iron porphyrins from functioning as a oxygen carrier we have discussed this umbrella thing we are talking do not write umbrella ok and this is just for explanation you can write if I am checking you can get marks if I am not you do not get marks so ok it prevents dimerization dimerization we have talked iron 2 plus and and 2 iron center can give 1 1 electron to the oxygen oxygen will be reduced to peroxide and this dimer formation see some of these term you must write if you if this question is asked the first thing will be it will it prevents dimerization even if you explain a lot of thing you do not say that it prevents dimerization you are not going to get the mark hopefully ok why CO is toxic we have discussed ah yes you know that while the cisplatin is potent anticancer agent it is trans isomer is not yes that is cisplatin that is transplatin transplatin and how it binds we were discussing right so see the 2 go on in for example are binding so actually sorry here actually chloride is going up going out ok alright ok so this is are you convinced are you convinced I do not think so ok are you convinced with the statement that the coordination complexes are capable of acting as drugs I think you better become convinced ok there are medicine I am sure some of you are taking or some of us are taking all of us are taking at some time of all life which has metal in it ok I think oh I forgot I do have jokes but I cannot tell you now but I leave you with this ok this is the last slide a message from you know alright