At the surfaces of proteins are amino acid residues that interact with water. The amino acids are referred to as hydrophilic amino acids and include arginine, lysine, aspartic acid, and glutamic acid. At pH 7 the side chains of these amino acids carry charges—positive for arginine and lysine, negative for aspartic acid and glutamic acid. As the pH increases, lysine and arginine begin to lose their positive charge, and at pHs greater than about 12 they are mainly neutral. In contrast, as pH decreases, aspartic acid and glutamic acid begin to lose their negative charges, and at pHs less than 4 they are mainly neutral.
The surface of a protein has a net charge that depends on the number and identities of the charged amino acids, and on pH. At a specific pH the positive and negative charges will balance and the net charge will be zero. This pH is called the isoelectric point, and for most proteins it occurs in the pH range of 5.5 to 8. A protein has its lowest solubility at its isoelectric point. If there is a charge at the protein surface, the protein prefers to interact with water, rather than with other protein molecules. This charge makes it more soluble. Without a net charge, protein-protein interactions and precipitation are more likely.
The solubility of proteins in blood requires a pH in the range of 7.35 to 7.45. The bicarbonate–carbonic acid buffer system of blood (HCO3− + H+ ↔ H2CO3), in which the bicarbonate is in excess of the carbonic acid, helps to maintain the correct pH. Exhalation of carbon dioxide from the lungs causes some of the bicarbonate ions in blood to combine with protons, and this would raise the pH. However, because there is an excess of bicarbonate ions and protons, the loss of a small number of protons does not influence the pH significantly.
The proteins of protein mixtures can be separated using a technique known as isoelectric focusing. A mixture is placed in a polyacrylamide gel that has a pH gradient. An anode (positive electrode) and a cathode (negative electrode) are positioned at the low and high ends of the pH gradient, respectively. If a protein is located in the high pH region, it will be negatively charged and will move toward the anode. As the protein moves to a lower pH region, its surface charge will become less negative, and a pH region will be reached at which the protein net charge is zero (the isoelectric point). The protein will stop moving and, because different proteins have different isoelectric points, separation can be achieved.
Over my head, and then some.....
but I appreciate the post.
Chen, does this unfold the clue as to why natural processing of sugars in a sourdough would prove more benefical to a diabetic, rather than a sugar that is processed chemically (derived by a non-natural state)?
I know this may seem a bit muddy. I'll espouse upon it if need be.
Thanks for revisiting the forum. I was taken aback with an earlier post when a source was not given credit, where credit was due. Please reference the article date and the author if the work is not an original. We want to acknowledge the author(s).
I appreciate your analysis.
One only needs moderate
One only needs moderate familiarity with Google and 10-15 minutes of spare time to realize that this person plagiarizes articles he finds on the net and crossposts them to various forums. This item, just like the last one has been stolen from http://www.chemistryexplained.com/Pr-Ro/Protein-Solubility.html
Mike
Suave, I'm a trusting sort....
not driven to check and double-check someones written word. My bad on this one. I truly do want to take someone at, 'their word', and at this point I can only ass u me that chen is one of two things; fearful that he/she doesn't have anything they can personally offer as their own writing, or, perhaps...and this is my choice, unaware of the legality of the issue at hand, and excited about sharing the knowledge.
Sooooooooooooooooooooooooo.......chen, I have a peace offering:
I'm understanding that you are ignorant of what is necessary when citing a public work. I stand guilty of this very thing myself. It took someone pointing it out to me before I could understand its value. This Internet business is a goldmine! So much information, so little time, but time is what we must slow a bit. Please, in the future, take the time to note where your resource material(s) come from, acknowledge the source by referencing the name of the book, title of the chapter, page notes and, when possible, the publish date.
We're all going somewhere in life. I'd like to think we can iron out the edges and find a way to understand a persons initiative. Ignorance is one thing, stupidity another. You are obviously far from being stupid, chen. If you can read a resource such as this one, understand it and share it, then your light bulbs are working. If you make a choice to deny a future reference their credit, well, then at that point WE are the stupid ones.
Oooh, I see now how it may
Oooh, I see now how it may seem I was referring to you. I wasn't and I sincerely apologize if I created an appearance I was. No, I was addressing the original poster, and if I sounded harsh it is only because in my sort of business this kind of thing is one of the biggest no-no's.
Mike
I'll add a comment to Grapevine's
After the last discussion of Chen's use of unattributed quotes, he said, ''It's only from the Web."
Chen, you may not understand that material on the Web is copyrighted. That means it belongs to the person who wrote it. You may not copy it and imply that it is your own, which is what you do imply when you do not give a citation.
As Grapevine points out, attribution (citing the source whether a book, a magazine, or a Website) is the ethical thing to do. It is also required by international copyright law.
Please benefit from our explanations. If you want to post someone else's work here, give a citation which discloses where you got the material.
Thank you.
Mary
Suave, put that whip down!
:)
;)
Interesting
As informative as that was, Chen, I am left wondering what your intentions are with these posts?
Apologies if I come across as overly hostile and suspicious but a brief google search shows that someone calling themselves 'chenhongxia' is a prolific poster of similarly-styled informational nuggets on many other food and science-related sites. (S)he apparently works for 'lookchem' which is the site linked through such posts. Presumably, these links are then picked up by Google and other web crawlers - thus bolstering the site's 'google presence'? Or put plainly - this is a form of spam.
I may be way off the mark here and I am truly sorry if that's the case but it does seem like a bit of a strange coincidence.
FP
One good point with a
One good point with a discussion about protein solubility might be to understand the difference between the unsoluble proteins in wheat "ie. gluten" and the soluble proteins in oats. This is why wheat is good for bread while oats are good for "milk replacement", if you understand what I mean by this; oat-milk etc.
The solubility of these proteins often dictate how much water something can bind, barley for exemple is especially poor in unsoluble protein especially the protein types that form gluten but due to the chemical composition of barley it can bind up to 6 times its own volume in water.
For those interested ni the geometrical shape of proteins a good rule of thumb is that soluble proteins are globular (spherical or similarly shaped) while unsoluble proteins are shaped more or less like strands, gluten for exemple. When heated soluble proteins can often change their characteristics due to heat denaturation and become elongated and unsoluble, this is what happens when you cook oatmeal porrige for exemple.
Btw. I have not read the original post so I dont know If all this can be accused of plagiarisation to but still, this might be of interest to someone I thought.