[Olivia james]

Hi
 Newbie here. I am trying to determine what criteria (atmospheric forces?) can damage an amino acid - heat, PH, Light, oxygen etc. As regards to heat for example, Aminos have a "melting point". Is this melting point the point of completion of the melting or the beginning? Do all of the components of the amino (hydrogen, nitrogen, carbon , etc) react to the heat in the same way. If one component reacts more readily than another, still then is the amino still that amino. If the amino threonine say, loses it's hydrogen component first in the melting process, and then the heat factor is removed, do we have an "injured" amino, or is the amino defunct by virtue of losing one of it's components.
  I apologize if this sounds a bit or a lot crazy, or poorly put - I am not a chem student but am curious as to the nature of chemical reactions etc.
                                                                                                                             Olivia

[discodermolide]

Hi
 Newbie here. I am trying to determine what criteria (atmospheric forces?) can damage an amino acid - heat, PH, Light, oxygen etc. As regards to heat for example, Aminos have a "melting point". Is this melting point the point of completion of the melting or the beginning? Do all of the components of the amino (hydrogen, nitrogen, carbon , etc) react to the heat in the same way. If one component reacts more readily than another, still then is the amino still that amino. If the amino threonine say, loses it's hydrogen component first in the melting process, and then the heat factor is removed, do we have an "injured" amino, or is the amino defunct by virtue of losing one of it's components.
  I apologize if this sounds a bit or a lot crazy, or poorly put - I am not a chem student but am curious as to the nature of chemical reactions etc.
                                                                                                                             Olivia

You are talking about a molecular property when you discuss melting point. The melting point is that temperature where all of the sample has liquified. Sometimes the melting of a compound leads to its decomposition, then the brown mess you get is no longer the substance you started with. In this case you have broken chemical bonds and perhaps made new ones.
Usually when you cool the melted compound you get the original compound back unchanged (chemically).

[Borek]

Melting point is a melting point. In the case of crystals melting point is not a range, but an exact temperature (just like ice melts at exactly 0°C).

You can't treat elements that the molecule is composed of as a independent components. When you remove a single atoms you get a different compound, usually with very different properties.

In other words - it is not like removing a wheel from the car - what is left is still a car, just without a wheel. It is more like after removing a wheel you get a TV set (although that would be a rare chemical gem, in most cases you will get just a vial full of poo).

[Olivia james]

 That is what I want to get at; at what point does a particular amino stop being that particular amino, with that amino's particular set of functions. If a circle is transformed into a square can we still call it a circle? It can no longer function as a circle. If in the case of the amino Threonine say which has the chemical makeup of C4 H9 N O3, if we eliminated any one of those components (or the value of one of the atoms?) will it still "function" as the amino Threonine? If so, at what point, how many parts do we have to remove before we all agree it can know longer act as the amino Threonine and do what threonine was biologically intended to do?
  As for "melting point", I still feel that there has to a kind of middle point, a stage in between solid and liquid. I am trying to determine if in that middle stage (or transition phase?) is it still at that stage either defunct or still useful. Like a protein has stages when heat is applied that can cause it to unfold and then refold (from primary to Quaternary and back) but not all stages can allow the protein to "perform" as it was designed to. And then, at what temperature will nothing perform, rendering the protein not just denatured but damaged beyond repair and renaturing. I want to apply that dynamic to the amino which is hardier perhaps than the collective of aminos known as proteins.  Thanx again guys

[Borek]

If in the case of the amino Threonine say which has the chemical makeup of C4 H9 N O3, if we eliminated any one of those components (or the value of one of the atoms?) will it still "function" as the amino Threonine?

I told you - no. You remove one atom and it is no longer Threonine.

As for "melting point", I still feel that there has to a kind of middle point, a stage in between solid and liquid.

You are mistaking an amorphic substance (like solid paraffin) for a crystalline substance (which a pure aminoacid is). In the case of the former there is no melting point, they get softer over the temperature range, which means they don't have a melting point. Crystalline substances have a melting POINT, which is - by definition - a point. It may happen they decompose before melting and we are not able to measure the melting point, but it doesn't mean they melt over the temperature range, it means what we observe is not melting.

[Olivia james]

Borek, thank you for your help. I got you when u said remove one atom and it changes etc - I just wanted to clarify to make sure I was both expressing myself clearly and understanding your answers clearly. I am also a newbie to chemistry and the science of aminos.
 I have found online, much information about the "degradation of amino acids" also known as "Amino acid catabolism". However, while the science websites exhibit the widest ranges of variables and factors that can "trigger the demise" of an amino or transform it into another amino (with an entirely different function) they are speaking of the dynamics within the body (the digestive processes etc).They also refer to these goings on's as "Controlled degradation of amino acids" -  something to do with the important maintenance of the carbon–nitrogen balance (). I am trying to determine which factors outside the body can change or completely degrade an amino. Perhaps the oxidative process which they speak of internally, can be a factor externally, as well as Ph balance impact.
  Granted if your body is not functioning properly to begin with, an amino can be impacted in the digestive process and in the liver and other parts and functions of the body - but that's a whole other discussion. I want to figure out which factors out side of the body, long before digestion and it's enzymes get to play their roles - like in a lab where they can do things to an amino to change it or completely destroy it - I want to know what those things are. Lets say I have a bowl of aminos and I squeeze the very acidic lemon into it - would that impact anything? Or oxygen? Or putting the bowl into the oven at 350 F ?? Or simple exposure to light?   thank you very much

[Babcock_Hall]

Some very general comments.  One, each amino acid is its own case, and some are much more easily damaged than others.  For example, when a protein is hydrolyzed in 6 molar hydrochloric acid, at least one amino acid, tryptophan, is destroyed.  The majority of the other common amino acids are not destroyed.  Cysteine is easily oxidized to other amino acids, some of which are not naturally occurring.

Two, it seems to me that there is a partial exception to the general rule that when we remove one atom, it is no longer threonine.  If I use a strong base to remove a proton from the form of threonine found at pH 6 from the nitrogen atom, I will make the conjugate base of threonine.  This new species does not have the same properties as its conjugate acid.  However, the two species are very closely related, and the process of removing or adding a proton is almost always reversible.  A proton is not the same thing as a hydrogen atom, of course.

Three, the process of melting a substance is not really like the process of heat denaturing a protein.  I would say in both instances the process might be reversible or not, but there the similarity ends.  When one denatures a protein by heat, the covalent structure of the protein is typically unchanged, but the conformation (shape) has been altered.  It is irreversible if the protein cannot find its biologically relevant conformation, the shape that confers its biological function.

Four, my comments about heat denaturation of a protein are pretty applicable to denaturation of a protein by extremes of pH.  The protein may or may not be irreversibly denatured.  On the other hand, it is rare that removal or addition of a proton to an amino acid causes an irreversible change, with the exception of tryptophan at high temperature, as noted above.  

I hope that my discussion clarifies some things.  It is certainly not my intention to nitpick.

[Olivia james]

Hi Babcock - thanx for your response. It's the nitpicking that I want/need. Even though I am not a chem person I can still sense generalizations. When one says an amino or protein may be renatured, I would like to know specifically at what point on the heat scale (temperature degree Celsius or Fahrenheit) would deem that protein damaged beyond repair (unable to refold). It's the generalities that impede my efforts to understand how we can damage proteins and aminos beyond the point of usefulness- so that I don't damage proteins and aminos.
  Hair has protein in it - if i lit a strand it would vaporize into the atmosphere. I couldn't reform those vapors into the original strand. I can't return cooked egg white to it's original clear gelatinous native state. Nor uncurdle my milk after putting lemons in it.
 I understand that I am crossing the bridge from proteins and aminos in the lab and science setting to those proteins and aminos in the kitchen setting but... A protein is a protein is a protein is it not, and when introduce to certain criteria it should react the same.
  Case in point - tryptophan. The lay person knows it as a thanksgiving dynamic that occurs when eating turkey (or too much turkey). I contend that that amino has been altered long before it reaches your plate by the process of food prepping with all manner of marinates (lemon, wine etc, salt) etc and then stuck in the oven four 4 hours at 400 degrees. i further contend that any big meal is going to leave one tired and ready for a nap and then football - especially when turkey day includes wines and beers.
                            Thanx again for your thoughts and anyone else's

[Borek]

I believe you are trying to run before learning how to walk. Details will only confuse you as long as you don't get a solid grasp of the basics.

[Olivia james]

A temperature is a detail and a basic issue. At what temperature is the refolding dynamic in a protein moot. If in a lab one exposes a protein to 100 degrees F and it starts to unfold (denature)after a few seconds and refolds when the heat source is removed, what happens when the heat is 200 degrees F and held for 2 minutes. Or 150 degrees F or 300 degrees F. If you know the basics the fundamentals of these things, it is those answers, in degrees F that I am interested in.
 If I am told that in fact, lemon juice is so acidic that it will denature my egg, beef or milk protein - I get that, and there is no confusion. Ceviche is meat protein being affected without heat. Death of most organisms includes a process of proteins being destroyed (by other enzymes) til there is no protein or meat remaining (bio degrading).
 I am trying overall, to get an understanding of how we damage our nutrients long before we consume them. Science dictates that so many factors go into protein and amino synthesis in the natural world - and conversely, so many factors can undo these nutrient molecules known as aminos and proteins. I am trying to determine which common factors that we never consider affect our nutrients.
  The reason I am on this forum as opposed to some food science forum(or body building, or food company forum), is that their view points are usually skewed and geared to serve their end, which is selling a product.
  Chemistry, I would hope has no agenda other than to state certain facts and not tweak those facts to sell anything. Food science  tweaks facts all the time. Food science tells me that you can light a protein to one thousand degrees and it will be just fine...   even an extremophile will be challenged if not vaporized at that point. Food science would never tell me like babcock did that one atom can/may change the ballgame. I appreciate that.

[Yggdrasil]

A few basic points that may be of help to you:

1)  Proteins are a chain of amino acids that are chemically bonded together.  As you have noted, these proteins fold up into a characteristic shape and this shape is important for the function of the protein.  Heating the protein, changing its chemical environment (e.g. altering the pH), and changes to many other conditions can cause these proteins to lose their characteristic shape (i.e. denature).  Denaturation, however, is a purely physical change to the protein's shape and it usually does not irreversibly alter the chemical composition of the protein.  In other words, even though the protein may not function anymore, the amino acids making up the protein remain intact.

As an analogy, consider a bead necklace as a protein.  It has a characteristic shape (a loop) which is important to its function.  Denaturing a protein is like cutting the necklace.  Since it is no longer a loop, a cut necklace can no longer perform its function even though the component beads that make up the necklace are unchanged by the "denaturation."

2) Our stomachs contain concentrated acid.  Therefore, when we consume proteins, the acid in our stomachs helps to denature the proteins.   The acid, along with enzymes in the digestive system, will break the protein down into its component amino acids.  These amino acids are then absorbed into the body where they can serve either as fuel for the body or as building blocks for new proteins.

To continue the necklace analogy, digestion in the stomach proceeds by denaturation (cutting the necklace string), which makes it easier to remove each individual bead from the necklace.  These beads can then be rearranged to form new necklaces, just as the amino acids from a digested protein can be used in the synthesis of new proteins.

Therefore, because proteins get denatured in our stomach, it does not matter whether the proteins we consumed are denatured or not prior to consumption.  Because denaturing an egg does not significantly alter the amino acids chemically, a cooked egg has the same nutritional content as a raw egg.  Therefore, most mild treatments (e.g. the acid in lemon juice), even though they might denature the proteins in food, will not irreversibly damage the amino acids in food.

One treatment that can, however, chemically alter the amino acids in proteins is high amounts of heat.  For example, the crust that forms when you sear a piece of meat is due to a chemical reaction between the sugars and proteins (the Maillard reaction), which does chemically alter the amino acids.  Here, I am not sure whether these changes can be reversed by the body, so these may have some effect on the nutritional content of the food.

[Olivia james]

Thank you for your reply. I get that the protein itself can and most likely will be damaged in most food prep and cooking dynamics yet still render the aminos intact - possibly. I get that acids, heat, light and oxygen will impact a protein - what I don't get is why marketing insists on saying then that beans cooked for an hour at boiling temps, or pasta or hot dogs and charbroiled fish etc has "protein". Do they not know the "protein" has been damaged?
  I also understand that an amino might be 'hardier' than the collective, the peptides, the chain of aminos. But science 101 tells us that a protein "must be in it's specific sequence put forth by god and DNA/RNA, to do a specific function." In order for a protein to do what it is biologically/specifically intended to do, then folded or unfolded or broken chains and otherwise damaged proteins won't be able to do that. Or why else would it matter to put forth the idea of proteins needing to be in a specific sequence?
  You mentioned that denaturing egg protein does not significantly alter the amino. "Significant" has to be defined, qualified and quantified. In this thread I was told the addition or subtraction of just one atom is all it takes to change an amino - in the case of Threonine for instance. If I am needing for some reason to get my threonine levels up say (I know it doesn't work that way , I'm just sayin), but if I did, then I no longer am getting Threonine if I have done something in the food prep process that might impact an atom.
  This is what I am ultimately trying to determine; the specifics at which we damage certain nutrients - in that I/we may stop damaging or "compromising" our nutrients. We are the only species that does this (another thread, another time). I am looking to determine at what point, what temperature, what level of acidity, how much and for how long will exposure to light and oxygen change the one atom or atoms that will make my amino no longer that amino.
  Aminos like proteins have specific functions, and if I am in need of that specific function I'm best served not messing with the atomic molecular structure of said amino. I like my burgers as much as the next guy, but plenty of the next guys think that their charbroiled burgers are sound sources of nutrients. Food science and it's cousin, Mr marketing, enables this way of thinking. I lean to science, and chemistry specifically, to say not so fast...
  If every kitchen had a electron microscope on the counter or a mass spectrometer in the pantry (and the skills to use it) we would all see first hand the myriad chemical reactions and changes that occur every second in the kitchen.
  I am not a lab person but I can't imagine that the atomic structural makeup of an egg protein or it's aminos, before cooking and after cooking are the same. Everything about a cooked egg is different from a raw egg; taste, texture, smell, look, mass - these are all molecular changes. How is the molecule that is a protein or the molecule that is an amino not altered? The reason we cook is to change molecules. The reason we marinate is to alter the molecular structure. Many of these molecular changes cannot be reversed - maybe in a careful lab setting can we add or subtract atoms but not in the barbecue pit. Thanx again for aiding in my quest to find a definitve

[Borek]

Proteins do get denatured and they lose their functions during cooking, but it doesn't matter much for nutrition. They are still proteins - chains of aminoacids. You can still digest them and cut them into aminoacids which are what you will ultimately absorb from the food and use in your own cells to synthesize proteins you need.

There is no simple answer to the question what are conditions that will destroy aminocid. Each aminoacid decomposes at different temperature, decomposition temperature is a function of pH, and aminoacids will behave differently when isolated and when in the polypeptide chain (to name just the most obvious things, I am sure there is more to it).

[DrCMS]

Having read through this thread it seems to me you are missing some important facts.

1) "amino" is not the same as "aminoacid" use the correct term for the material you are discussing.
2) if you chemically alter a specific aminoacid by heat, oxidation etc then it is no longer than particular amino acid anymore but it can be used as fuel by the human body.
3) we eat proteins but not because we use that protein to do a job but instead our body break it down into the aminoacids it was made from and we use those aminoacids to make the proteins we need to function.
4) our digestive system denatures the proteins we eat as part of the process of breaking them apart into aminoacids
5) cooking will also denature the proteins and that actually makes digesting them into the aminoacids easier (it is though this may be how our brain size increased so much compared to our ape cousins.

[fledarmus]

Proteins do not get absorbed into the body whole. When people talk about the "protein content" of a food source, what they are really referring to is amino acids. In the stomach, the proteins are digested and the amide bonds between the amino acids are hydrolyzed. The free amino acids are then transported through the stomach wall by active amino-acid transporters. These amino acids are then used by the cell machinery to synthesis whatever proteins the human body needs.

The problem is that proteins may have chemical effects that the body does not want and cannot tolerate. The individual amino acids which make up the proteins don't have those chemical effects and can be safely absorbed. A lot of the machinery in your gut is designed to break down very large chemical structures like proteins into useful building blocks that are too small to have the same biological activities.

For a protein to exhibit its biological activity, it must be folded into the right shape. If you go to the protein data bank you can download some lovely 3-D pictures of the enzymes, many hundreds of amino acids long, folded into their active conformations. Other functionalities may also need to be attached to various specific amino acids in the protein to make it work in the body - phosphates, sugars, farnesyl groups, and many other small molecules may be attached to the protein to get the specific form that the body needs. Imagine making twenty different balls of string and having every single one formed exactly the same? That is the sort of reproducibility the body needs to make an active protein.

The individual sequence of amino acids gives some help to the process. Particular sequences tend to fold automatically into particular shapes. For example, sequences which contain mostly very small side chains like glycine or alanine tend to fold into nice helical spirals. These structures are very useful for making proteins which need to support weight, like collagen and keratin. Cross-links can also be made from sidechains on one piece of the protein to side chains on another, to glue the ball of string into the right conformation. Cysteines are particularly good at this - the sulfur on the end of the side chain on one cysteine can find the sulfur on another cysteine on a different part of the protein and form disulfide bonds.

The exact shape of the protein that the body needs for its uses is called the "natural" form. Deviations from that form that make the protein no longer useful for its intended purpose are called "denatured" proteins. This can be very slight - for instance, acidic side chains like on aspartic and glutamic acids frequently interact with basic side chains like on lysine or arginine to hold parts of the protein in place. If you add hydrochloric acid, it may attach to the lysine and arginine and prevent it from attaching to acidic side groups, partially unfolded that part of the ball of string. This may be reversible - adding a base or even a buffer may be enough to return the protein to its natural conformation. In other cases, the process may go further - adding a reducing agent to keratin for example, will break the cysteine disulfide bonds, which can be reformed by adding an oxidizing agent. In the process of perming hair, the hair is rinsed with a reducing agent to break all the bonds, the hair is formed into the shape that you want it to hold, and an oxidizing agent is added to reform the cysteine bonds, locking the hair into its new shape.

Other denaturation processes are more permanent. Many times, a protein only achieves its natural conformation because other proteins, so-called chaperone proteins, fold it into the proper shape. When these compounds are heated to the point where they lose their shape, they will rarely refold back into the natural configuration. Strong acids and bases, lots of heat, and digestive enzymes will actually separate the amino acids from one another, clipping the protein into smaller pieces. Eventually it can be clipped all the way down to its component amino acids, ready for reuse in building new proteins.

So that is a very brief overview of protein shape, which is what denaturing changes. I hope you find it helpful.


Just one request - you are on a chemistry board. Please begin using the term "amino acids" and stop using "aminos" to refer to those structures. Amino acids, which are the components of proteins, have an amine group and a carboxylic acid group. It is the presence of those two groups which make it possible for them to form the long chains of amide-linked compounds that form proteins. "Aminos" is not a chemical term describing anything - our closest equivalent is "amines" which are compounds which have an amine group.