tag:blogger.com,1999:blog-44846629405387551452024-02-20T17:47:12.659-08:00PROTEINS AND PEPTIDESAnonymoushttp://www.blogger.com/profile/06267357132580929345noreply@blogger.comBlogger1125tag:blogger.com,1999:blog-4484662940538755145.post-90953321318476511552013-11-02T08:51:00.002-07:002013-11-02T08:52:36.638-07:00PROTEIN AND PEPTIDES<div dir="ltr" style="text-align: left;" trbidi="on">
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<span style="color: maroon; font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Peptides & Proteins<o:p></o:p></span></h2>
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<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">1. The Peptide Bond<o:p></o:p></span></h3>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">If the amine and carboxylic acid functional groups in
amino acids join together to form amide bonds, a chain of amino acid units,
called a <b>peptide</b>, is formed. A simple tetrapeptide structure is shown in
the following diagram. By convention, the amino acid component retaining a free
amine group is drawn at the left end (the N-terminus) of the peptide chain, and
the amino acid retaining a free carboxylic acid is drawn on the right (the
C-terminus). As expected, the free amine and carboxylic acid functions on a
peptide chain form a zwitterionic structure at their isoelectric pH. <br />
By clicking the "<u><span style="color: brown;">Grow Peptide</span></u>"
button, an animation showing the assembly of this peptide will be displayed.
The "<u><span style="color: brown;">Show Structure</span></u>" button
displays some bond angles and lengths that are characteristic of these
compounds.<o:p></o:p></span><br />
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<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The conformational flexibility of peptide chains is
limited chiefly to rotations about the bonds leading to the alpha-carbon atoms.
This restriction is due to the rigid nature of the amide (peptide) bond. As
shown in the following diagram, nitrogen electron pair delocalization into the
carbonyl group results in significant double bond character between the
carbonyl carbon and the nitrogen. This keeps the peptide links relatively
planar and resistant to conformational change. The color shaded rectangles in
the lower structure define these regions, and identify the relatively facile
rotations that may take place where the corners meet (i.e. at the
alpha-carbon). This aspect of peptide structure is an important factor
influencing the conformations adopted by proteins and large peptides.<o:p></o:p></span><br />
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<h3>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">2. The Primary Structure of Peptides <o:p></o:p></span></h3>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Because the N-terminus of a peptide chain is distict
from the C-terminus, a small peptide composed of different aminoacids may have
a several constitutional isomers. For example, a dipeptide made from two different
amino acids may have two different structures. Thus, aspartic acid (Asp) and
phenylalanine (Phe) may be combined to make Asp-Phe or Phe-Asp, remember that
the amino acid on the left is the N-terminus. The methyl ester of the first
dipeptide (structure on the right) is the artificial sweetner <b>aspartame</b>,
which is nearly 200 times sweeter than sucrose. Neither of the component amino
acids is sweet (Phe is actually bitter), and derivatives of the other dipeptide
(Phe-Asp) are not sweet. <br />
A tripeptide composed of three different amino acids can be made in 6 different
constitutions, and the tetrapeptide shown above (composed of four different
amino acids) would have 24 constitutional isomers. When all twenty of the
natural amino acids are possible components of a peptide, the possible
combinations are enormous. Simple statistical probability indicates that the
decapeptides made up from all possible combinations of these amino acids would
total 20<sup>10</sup>!<o:p></o:p></span><br />
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Natural peptides of varying complexity are abundant.
The simple and widely distributed tripeptide glutathione (first entry in the
following table), is interesting because the side-chain carboxyl function of
the N-terminal glutamic acid is used for the peptide bond. An N-terminal
glutamic acid may also close to a lactam ring, as in the case of TRH (second
entry). The abbreviation for this transformed unit is pGlu (or pE), where p
stands for "pyro" (such ring closures often occur on heating). The
larger peptides in the table also demonstrate the importance of amino acid
abbreviations, since a full structural formula for a nonapeptide (or larger)
would prove to be complex and unwieldy. The formulas using single letter
abbreviations are colored red.<br />
The ten peptides listed in this table make use of all twenty common amino
acids. Note that the C-terminal unit has the form of an amide in some cases
(e.g. TRH, angiotensin & oxytocin). When two or more cysteines are present
in a peptide chain, they are often joined by <a href="http://www.cem.msu.edu/~reusch/VirtualText/proteins.htm#aacd4b">disulfide
bonds</a> (e.g. oxytocin & endothelin); and in the case of insulin, two
separate peptide chains (A & B) are held together by such links.<o:p></o:p></span><br />
<a href="http://www.blogger.com/blogger.g?blogID=4484662940538755145" name="aacd6c"></a><a href="http://www.blogger.com/blogger.g?blogID=4484662940538755145" name="aacd6d"></a><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The
different amino acids that make up a peptide or protein, and the order in which
they are joined together by peptide bonds is referred to as the <b>primary
structure</b>. From the examples shown above, it should be evident that it is
not a trivial task to determine the primary structure of such compounds, even
modestly sized ones. <br />
Complete hydrolysis of a protein or peptide, followed by amino acid analysis
establishes its gross composition, but does not provide any bonding sequence
information. <o:p></o:p></span><br />
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</v:shape><![endif]--><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Partial hydrolysis will produce a mixture of shorter
peptides and some amino acids. If the primary structures of these fragments are
known, it is sometimes possible to deduce part or all of the original structure
by taking advantage of overlapping pieces. For example, if a heptapeptide was
composed of three glycines, two alanines, a leucine and a valine, many possible
primary structures could be written. On the other hand, if partial hydrolysis
gave two known tripeptide and two known dipeptide fragments, as shown on the
right, simple analysis of the overlapping units identifies the original primary
structure. Of course, this kind of structure determination is very inefficient
and unreliable. First, we need to know the structures of all the overlapping
fragments. Second, larger peptides would give complex mixtures which would have
to be separated and painstakingly examined to find suitable pieces for
overlapping. It should be noted, however, that modern mass spectrometry uses
this overlap technique effectively. The difference is that bond cleavage is not
achieved by hydrolysis, and computers assume the time consuming task of
comparing a multitude of fragments.<o:p></o:p></span><br />
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<span style="color: maroon; font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Structure-Property Relationships<o:p></o:p></span></h3>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The compounds we call proteins exhibit a broad range
of physical and biological properties. Two general categories of simple
proteins are commonly recognized.<o:p></o:p></span><br />
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<b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Fibrous
Proteins<o:p></o:p></span></b></div>
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<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"> <o:p></o:p></span></div>
</td>
<td nowrap="" style="padding: .75pt .75pt .75pt .75pt; width: 438.05pt;" valign="top" width="730"><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">As the name implies, these substances have
fibre-like structures, and serve as the chief structural material in various
tissues. <br />
Corresponding to this structural function, they are relatively insoluble in
water and unaffected by moderate changes in temperature and pH. <br />
Subgroups within this category include:<br />
<u>Collagens & Elastins</u>, the proteins of
connective tissues. tendons and ligaments.<br />
<u>Keratins</u>, proteins that are major components of
skin, hair, feathers and horn.<br />
<u>Fibrin</u>, a protein formed when blood clots.<o:p></o:p></span></td>
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<b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Globular
Proteins<o:p></o:p></span></b></div>
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<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"> <o:p></o:p></span></div>
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<td nowrap="" style="padding: .75pt .75pt .75pt .75pt; width: 438.05pt;" valign="top" width="730"><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Members of this class serve regulatory, maintenance
and catalytic roles in living organisms. <br />
They include hormones, antibodies and enzymes. and either dissolve or form
colloidal suspensions in water. <br />
Such proteins are generally more sensitive to temperature and pH change than
their fibrous counterparts.<o:p></o:p></span></td>
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<h3>
<a href="http://www.blogger.com/blogger.g?blogID=4484662940538755145" name="aacd7a"></a><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">1. The Secondary and Tertiary Structure of Large
Peptides and Proteins<o:p></o:p></span></h3>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The various properties of peptides and proteins depend
not only on their component amino acids and their bonding sequence in peptide
chains, but also on the way in which the peptide chains are stretched, coiled
and folded in space. Because of their size, the orientational options open to
these macromolecules might seem nearly infinite. Fortunately, several factors
act to narrow the structural options, and it is possible to identify some
common structural themes or <b>secondary structures</b> that appear repeatedly
in different molecules. These conformational segments are sometimes described
by the dihedral angles , defined in the diagram on the right below. Most
proteins and large peptides do not adopt completely uniform conformations, and
full descriptions of their preferred three dimensional arrangements are defined
as <b>tertiary structures</b>. <o:p></o:p></span><br />
<h4 style="margin-left: .5in;">
<a href="http://www.blogger.com/blogger.g?blogID=4484662940538755145" name="aacd7b"></a><span style="color: maroon; font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">A. Helical Coiling</span><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></h4>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The relatively simple undecapeptide shown in the
following diagram can adopt a zig-zag linear conformation, as drawn. A ball
& stick model of this peptide will be displayed by clicking the appropriate
button. However, this molecule prefers to assume a coiled helical conformation,
displayed by clicking any of the three buttons on the right. The middle button
shows a stick model of this helix, with the backbone chain drawn as a heavy
black line and the hydrogen bonds as dashed maroon lines. The other buttons
display a ball & stick model and a ribbon that defines this <b>-helix</b>.
Seven hydrogen bonds, that together provide roughly 30 kcal/mol stability, help
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<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Examine the drawing activated by the middle button.
The N-terminal residue (Ala) is on the left, and the C-terminal Gly on the
right. The alpha-helix is right-handed, which means that it rotates clockwise
as it spirals away from a viewer at either end. Other structural features that
define an alpha-helix are: the relative locations of the donor and acceptor
atoms of the hydrogen bond, the number of amino acid units per helical turn and
the distance the turn occupies along the helical axis. The first hydrogen bond
(from the N-terminal end) is from the carbonyl group of the alanine to the N-H
group of the phenylalanine. Three amino acids, Thr, Gly & Ala, fall
entirely within this turn. Parts of the N-terminal alanine acceptor and the
phenylalanine donor also fall within this helical turn, and careful analysis of
the structure indicates there are 3.6 amino acid units per turn. The distance
covered by the turn is 5.4 Å. Using the dihedral angle terminology noted above,
a perfect -helix has = -58º and = -47º. In natural proteins the values
associated with -helical conformations range from -57 to -70º for , and from
-35 to -48º for . To examine a Chime model of this alpha-helix, click on the
green circle.<br />
Helical conformations of peptide chains may also be described by a two number
term, <b>n<sub>m</sub></b>, where <b>n</b> is the number of amino acid units
per turn and <b>m</b> is the number of atoms in the smallest ring defined by
the hydrogen bond. Using this terminology, the alpha-helix is a 3.6<sub>13</sub>
helix. Other common helical conformations are 3<sub>10</sub> and 4.4<sub>16</sub>.
The alpha helix is the most stable of these, accounting for a third of the
secondary structure found in most globular (non-fibrous) proteins. <o:p></o:p></span><br />
<h4 style="margin-left: .5in;">
<a href="http://www.blogger.com/blogger.g?blogID=4484662940538755145" name="aacd7c"></a><span style="color: maroon; font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">B. -Pleated Sheets</span><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></h4>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The linear zig-zag conformation of a peptide chain may
be stabilized by hydrogen bonding to adjacent parallel chains of the same kind.
Bulky side-chain substituents destabilize this arrangement due to steric
crowding, so this <b>beta-sheet</b> conformation is usually limited to peptides
having a large amount of glycine and alanine. Steric interactions also cause a
slight bending or contraction of the peptide chains, and this results in a
puckered distortion (the pleated sheet). As shown in the following diagram, the
adjacent chains may be oriented in opposite N to C directions, termed <b>antiparallel</b>.
Using the dihedral angle terminology, an antiparallel -sheet has = -139º and
a = 135º. Alternatively, the adjacent peptide chains may be oriented in the
same direction, termed <b>parallel</b>. By convention, beta-sheets are
designated by broad arrows or cartoons, pointing in the direction of the
C-terminus. In this diagram, these cartoons (colored violet) are displayed by
clicking on the appropriate button. A Chime model of a this
three-antiparallel-chain structure may be examined by clicking on the green
circle. <o:p></o:p></span><br />
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<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The main protein component of silk, fibroin, adopts a
beta-pleated sheet secondary structure, a small segment of which may be
examined in the Chime model. Silk fibroin is 40-45% Gly, 27-33% Ala, and
roughly equal amounts (12-15%) of Ser and Thr. Filaments of silk are
particularly thin and uniform in structure.<br />
When beta-sheets are observed as secondary structural components of globular
proteins, they are twisted by about 5 to 25º per residue; consequently, the
planes of the sheets are not parallel. The twist is always of the same
handedness, and is usually greater for antiparallel sheets. Examples will be
found in the following structures.<o:p></o:p></span><br />
<div class="MsoNormal">
<br /></div>
<h4 style="margin-left: .5in;">
<span style="color: maroon; font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">C. Other Structures</span><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></h4>
<a href="http://www.blogger.com/blogger.g?blogID=4484662940538755145" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Although most proteins and large peptides may have
alpha-helix and beta-sheet segments, their tertiary structures may consist of
less highly organized turns, strands and coils. <b>Turns</b> reverse the
direction of the peptide chain, and are considered to be a third common
secondary structure motif. Approximately a third of all the residues in
globular proteins are found in turns. Turns occur chiefly on the protein
surface, often incorporate polar and charged residues, and have been classified
in three sub-groups. <br />
<a href="http://www.cem.msu.edu/~reusch/VirtualText/protein2.htm#aacd7">As
noted earlier</a>, several factors perturb the organization of peptide chains.
One that has not yet been cited is the structural influence of proline. Unlike
the other common amino acids, rotation about the C-N bond in proline is not
possible due to the structural constraint of the five-membered ring.
Consequently, the presence of a proline in a peptide chain introduces a bend or
kink that disrupts helices or sheets. Also, prolines that are part of a peptide
chain have no N-H hydrogen bonding donors to contribute to conformer
stabilization.<br />
With the exception of silk fibroin and certain synthetically engineered
peptides, significant portions of most proteins adopt conformations that resist
simple description or categorization. For example, the following diagram shows
the tertiary structure of a polypeptide found in cobra venom. A large section
of antiparallel beta-sheets is colored violet, and a short alpha-helix is
green. The remaining peptide chain seems disorganized, but certain recurring
features such as seven 180º turns (beta-turns) and five disulfide bonds can be
identified. A Chime model of this compound may be examined <span style="color: brown;">by clicking on the diagram</span>.<o:p></o:p></span><br />
<div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></div>
<div align="center" style="text-align: center;">
<br /></div>
<div class="MsoNormal">
<br /></div>
<h4>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Additional Examples<o:p></o:p></span></h4>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">A full description and discussion of protein structure
is beyond the scope of this text, but a few additional examples will be
instructive. In addition to the tertiary structures that will be displayed,
attention must also be given to the way in which peptide structures may
aggregate to form dimeric, trimeric and tetrameric clusters. These assemblies,
known as <b>quaternary structures</b>, have characteristic properties different
from their monomeric components. The examples of mellitin, collagen and
hemoglobin, shown below demonstrate this feature.<br />
Some proteins incorporate nonpeptide molecules in their overall structure,
either bonded covalently or positioned by other forces. These are called <b>conjugated
proteins</b>, and the non-peptide components are referred to as <b>prosthetic
groups</b>. Examples of conjugated proteins include:<o:p></o:p></span><br />
<div style="margin-left: .5in;">
<b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Glycoproteins</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">,
incorporating polysaccharide prosthetic groups (e.g. collagen and mucus).<br />
<b>Lipoproteins</b>, incorporating lipid prosthetic groups (e.g. HDL and LDL).<br />
<b>Chromoproteins</b>, incorporating colored prosthetic groups (e.g. hemoglobin).<o:p></o:p></span></div>
<b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The seven illustrations shown below identify a set of
peptides and proteins that may be examined as Chime models <span style="color: brown;">by clicking on a selected picture</span>.</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span><br />
<div style="margin-left: .5in;">
<b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Endothelin & Angiogenin</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"> are small peptides that have important and selective
physiological properties.<br />
<b>Lysozyme</b> a typical globular protein, incorporating many identifiable
secondary structures.<br />
<b>Mellitin</b>, from honey bee venom, has a well-defined quaternary structure,
half of which is shown here.<br />
<b>Collagen</b> is a widely distributed fibrous protein with a large and
complex quaternary structure. Only a small model segment is shown here.<br />
<b>Thioredoxin</b> is a relatively small regulatory protein serving an
important redox function.<br />
<b>Hemoglobin</b>, the most complex of these examples, is a large conjugated
protein that transports oxygen. A 170 pound human has about a kilogram of
hemoglobin distributed among some five billion red blood cells. A liter of
arterial blood at body temperature can transport over 200 mL of oxygen, whereas
the same fluid stripped of its hemoglobin will carry only 2 to 3 mL.<o:p></o:p></span></div>
<h3 align="center" style="text-align: center;">
<span style="color: maroon; font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Denaturation<o:p></o:p></span></h3>
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">The natural or native structures of proteins may be
altered, and their biological activity changed or destroyed by treatment that
does not disrupt the primary structure. This <b>denaturation</b> is often done
deliberately in the course of separating and purifying proteins. For example,
many soluble globular proteins precipitate if the pH of the solution is set at
the pI of the protein. Also, addition of trichloroacetic acid or the bis-amide
urea (NH<sub>2</sub>CONH<sub>2</sub>) is commonly used to effect protein
precipitation. Following denaturation, some proteins will return to their
native structures under proper conditions; but extreme conditions, such as
strong heating, usually cause irreversible change.<br />
Some treatments known to denature proteins are listed in the following table.<o:p></o:p></span><br />
<div align="center">
<table border="0" cellpadding="0" cellspacing="3" class="MsoNormalTable">
<tbody>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" width="245"><h3 align="center" style="text-align: center;">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Denaturing
Action<o:p></o:p></span></h3>
</td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" width="592"><h3 align="center" style="text-align: center;">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Mechanism
of Operation<o:p></o:p></span></h3>
</td>
</tr>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" valign="top" width="245"><b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Heat</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" valign="top" width="592"><div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">hydrogen bonds are broken by increased translational
and vibrational energy.<br />
(coagulation of egg white albumin on frying.)<o:p></o:p></span></div>
</td>
</tr>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" valign="top" width="245"><b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Ultraviolet Radiation</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" valign="top" width="592"><div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Similar to heat</span><span lang="RU" style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: RU;"> </span><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">(sunburn)<o:p></o:p></span></div>
</td>
</tr>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" valign="top" width="245"><b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Strong Acids or Bases</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" valign="top" width="592"><div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">salt formation; disruption of hydrogen bonds.<br />
(skin blisters and burns, protein precipitation.)<o:p></o:p></span></div>
</td>
</tr>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" valign="top" width="245"><b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Urea Solution</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" valign="top" width="592"><div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">competition for hydrogen bonds.<br />
(precipitation of soluble proteins.)<o:p></o:p></span></div>
</td>
</tr>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" valign="top" width="245"><b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Some Organic Solvents</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><br />
(e.g. ethanol & acetone)<o:p></o:p></span></td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" valign="top" width="592"><div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">change in dielectric constant and hydration of ionic
groups.<br />
(disinfectant action and precipitation of protein.)<o:p></o:p></span></div>
</td>
</tr>
<tr>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 147.0pt;" valign="top" width="245"><b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">Agitation</span></b><span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;"><o:p></o:p></span></td>
<td style="padding: 3.75pt 3.75pt 3.75pt 3.75pt; width: 355.05pt;" valign="top" width="592"><div class="MsoNormal">
<span style="font-family: "Copperplate Gothic Bold","sans-serif"; font-size: 16.0pt; mso-ansi-language: EN-US;">shearing of hydrogen bonds.<br />
(beating egg white albumin into a meringue.)<o:p></o:p></span></div>
</td>
</tr>
</tbody></table>
</div>
</form>
</div>
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