Posted: 06 February 2010 at 7:44pm | IP Logged

What is meant by peptization or salting-in of a peptide?  Why is there so much controversy about the process?  The term goes back to the studies of colloidial properties of matter during the last century or so!  In the 1934 classic text ("Colloids") by Arthur Thomas, a  contemporaryof our own great Arthur Wilson, he states:  "When gels are converted to sols by the influence of added foreign substances, a reaction takes place which resembles in apperance the peptonizing of proteins in animal digestion and consequently was named peptinization (now shortened to peptization) by Graham." 

What does salting-in mean to tanners?  Certainly the process of dissolving proteins in saline solutions with subsequent precipitation as more salt is added,has been employed by chemists for several centuries to purify proteins.  Salting-out has been used and often the solubility curves for proteins by various types of salts has typical  parabolic shapes well known to all.  Why do low concentrations help dissolve and high concentrations coagulate?

Posted: 09 February 2010 at 10:35am | IP Logged

There we go again

You got up on the Jell-O side of the bed today, again, David.

Please show me today were is that big controversy.

Regards

Zercas

Posted: 09 February 2010 at 10:56am | IP Logged

Here is an "archeological paper", David.

http://www3.interscience.wiley.com/journal/119774697/abstrac t?CRETRY=1&SRETRY=0

Regards

Zercas

Posted: 09 February 2010 at 11:31am | IP Logged

Enjoy this one David, but Collagen mentined there.

http://www.rsc.org/ebooks/archive/free/BK9780851864433/BK978 0851864433-00001.pdf

Regards

Zercas

Posted: 09 February 2010 at 5:52pm | IP Logged

David

Let us settle this issue once and for all, it is the way you look at reality. This is an extract of Covington's new book, there is no mention of collagen as colloid, I posted the two references he mentions in this small  paragraph.

  Covington's  Tanning Chemistry : The Science of leather

 Page 24   2009  ( The latest in Leather Technology !!!!!!! )

Collagen has been described in terms of a block copolymer, incorporating hard and soft monomeric units, (45) in which there are crystalline regions, associated with the presence of hydroxyproline ,  (46) where the protein structure is supported by the supramolecular water.

Ref. (45) http://www.nature.com/nature/journal/v174/n4442/abs/1741142a 0.html

Ref. (46)

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi =B6WM5-45M7TPH-9&_user=10&_coverDate=12%2F31%2F1998& amp; amp;_rdoc=1&_fmt=high&_orig=search&_sort=d&_ docanchor=&view=c&_searchStrId=1200714948&_rerun Origin=google&_acct=C000050221&_version=1&_urlVe rsion=0&_userid=10&md5=f7f632a649d351788369413e71196 475

 Those segments, that you stick to call them "gelatine molecules " (?)

are linked together by covalent bonds, NO PARTICLES, NO COLLOID, NO CMC (Critical Micelle Concentration ).

I respect your opinions in many other areas and subjects, but your Jell-O theory in the leather technology I belive is just an illusion in your mind.

Regards

Zercas

Posted: 09 February 2010 at 6:40pm | IP Logged

Terminology is fickle and changes with time.  At one point in history (not so long ago, maybe 30 to 50 years) leather chemistry was almost entirely consumed with the colloid chemistry idea.  Many papers were written and new advances jumped from the new line of reasoning.  Certainly the concept takes a stretch of the imagination, yet no other concept at the time could take into account the compexity and uniqueness of the collagen matrix so intensely active with water and salts, not to mention a plethora of other proteins, carbohydrates and fats.  While I love to jab at David to make him think and explain his strong feelings for these colloidal expressions, I deeply appreciate the connection to real chemical and physical relationships in skin, leather and, yes, gelatin. 

As you have noted, tanners have been using "nano" technology for centuries, yet the term has only recently been applied to real process ideas.  Soon that term will wear out its appeal and something new with hit the streets, just as colloids no longer get much press, though the concept is still meaningful.