Quiet Loner Soul

PNS

• • nerve fibres regenerate depending on their location

• • Schwann cells guide the regeneration of cut axons

CNS

• • repair and functional regeneration is limited

  • myelin associated inhibitory factors

  • astrocyte scar formation and age related decline in repair mechanisms

Spinal Cord Damage

• • mainly due to cell death, inflammation, expanding cysts and glial scarring, also degenerating tracts, demylination and atrophied muscles

  • some spontaneous repair – gliogenesis, sprouting axons, cortical sensory motor arrangement, some rubriospinal compensation

  • prevents expansion of critical damage, create bridges, promote axon regeneration, compensate for demylination, replace dead cells

  • parapligia or quadriplegia

Parkinson’s Disease

• • disordered control over movements

  • loss of dopaminergic neurons in pars compacta of substancia nigra

  • actions - increase L-dopa, inhibit degradation by MAO-B, stimulate release of dopamine, block action of Ach in striatum

  • mechanisms – overactive glutamate producing cells affected by free radicals

Stem Cells

• • stem/progenitor cells are self renewing and can be used for gene therapy

  • can differentiate into neurons or glia

  • neurosphere – a clone of cells from a single neural stem cells (multipotent)

  • can be treated with factors for promoting neural differentiation

Other Pathways

• • growth and migration factors

  • functional integration (axon growth and guidance molecules)

  • increase in the number of neurons

<!– /* Font Definitions */ @font-face {font-family:Wingdings; panose-1:5 0 0 0 0 0 0 0 0 0; mso-font-charset:2; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:0 268435456 0 0 -2147483648 0;} @font-face {font-family:”Cambria Math”; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:1; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:”"; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:”Times New Roman”,”serif”; mso-fareast-font-family:”Times New Roman”;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:595.3pt 841.9pt; margin:1.0in 1.25in 1.0in 1.25in; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} /* List Definitions */ @list l0 {mso-list-id:440732915; mso-list-type:hybrid; mso-list-template-ids:-893635146 201916431 201916441 201916443 201916431 201916441 201916443 201916431 201916441 201916443;} @list l0:level1 {mso-level-tab-stop:.5in; mso-level-number-position:left; text-indent:-.25in;} @list l1 {mso-list-id:1417090093; mso-list-type:hybrid; mso-list-template-ids:2112792474 201916431 201916441 201916443 201916431 201916441 201916443 201916431 201916441 201916443;} @list l1:level1 {mso-level-tab-stop:.5in; mso-level-number-position:left; text-indent:-.25in;} @list l1:level2 {mso-level-number-format:alpha-lower; mso-level-tab-stop:1.0in; mso-level-number-position:left; text-indent:-.25in;} ol {margin-bottom:0in;} ul {margin-bottom:0in;} –>

Carbohydrate Catabolism

1. During the preparatory stage of glycolysis, the molecule of glucose is phosphorylated, and converted into two molecules of glyceraldehyde-3-phosphate. This requires the use of two ATP molecules.

In the payoff phase, the glyceraldehyde-3-phosphate is converted to pyruvate. This releases four ATP molecules, and produces two NADH molecules.

1. In the preparatory phase the phosphate groups are obtained from 2 ATP and attached in place of the OH groups, producing glyceraldehyde-3-phosphate, and leaving 2 ADP molecules behind.

In the pay-off phase, a molecule of Pi replaces the H group, releasing electrons to form NADH and 1,3-biphosphoglycerate. The phosphate group is then removed by ADP to form ATP and 3-phosphoglycerate.

1. Substrate-level phosphorylation is the transfer of a high energy phosphate group from 1,3-biphosphoylate/phosphoenolpyruvate to ADP to produce ATP and a molecule of 3-phosphoglycerate/pyruvate.

1. Although the conversion of glucose to glucose-6-phosphate is endergonic (requires energy, in the form of 2 ATP molecules), the overall process of glycolysis still proceeds. This is because the overall reaction is exogonic, and the later stages have excess energy to help the first reactions proceed.

1. For humans, pyruvate has two possible metabolic fates. In anaerobic conditions, such as during a sprint, pyruvate undergoes fermentation (in active skeletal muscle, the retina or red blood cells) to produce lactate and ATP. This method of producing energy is very inefficient compared to the energy produced under aerobic conditions. In aerobic conditions, during everyday cellular respiration, pyruvate is further oxidised to form the eventual products of carbon dioxide and water.

Lipid Catabolism

1. There are six steps in the digestion and transport of dietary lipids to adipose tissue.
   1. In the small intestine fat is emulsified by bile salts secreted from the gall bladder to produce mixed micelles.
   2. Triacylglycerols within the mixed micelles are degraded by intestinal lipases into monoacylglycerols, diacylglycerols, free fatty acids and glycerol.
   3. These products then diffuse into the epithelium cells lining the intestinal surface where they are reconverted into triacylglycerols.
   4. The insoluable triacylglycerols are packaged with phospholipids, proteins and cholesterol to form chylomicrons. Chylomicrons then move from the epithelial cells into the lymphatic system, where they can enter the bloodstream.
   5. The chylomicrons move through the bloodstream until the reach adipose tissue. They are then degraded into their original parts (releasing free fatty acids and glycerol) within the capillaries of the adipose tissue.
   6. The freed fatty acids are taken up by the cells, where they are reesterified for storage as triacylglycerols.

The mobilisation of stored lipids maintains the body’s energy levels during starvation (both long term and between meals). Low glucose levels in the blood cause the release of hormones which activate the enzyme triacylglycerol lipase. This stimulates the breakdown of stored fatty acids into fatty acids and glycerol – the fatty acids are transported by serum albumin to the muscles and the glycerol is recycled back to the liver. This is basically the reverse of the fats original breakdown.

1. The CoA pool in the intermembrane space provides the CoA required to generate the first stage Fatty Acyl-CoA from a fatty acid. CoA is then replaced by carnitine so that the fatty acid can pass across the membrane. The second pool of CoA releases the carnitine (to pass back into the intermembrane space) and regenerates Fatty Acyl-CoA. The carnitine prevents the two pools from interacting because it is the only thing allowed across the membrane.
2. The four reactions of B-oxidation are: oxidation, hydration, another oxidation and thiolytic cleavage.
3. Reduced electron carriers are generated by reaction 1 (FAD à FADH) and reaction 3 (NAD+ à NADH).

<!– /* Font Definitions */ @font-face {font-family:”Cambria Math”; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:1; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:”"; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:”Times New Roman”,”serif”; mso-fareast-font-family:”Times New Roman”;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in; mso-header-margin:.5in; mso-footer-margin:.5in; mso-paper-source:0;} div.Section1 {page:Section1;} –>

Five possible fates for glucose 6-phosphate in the liver are:

1. being oxidised via glycolysis, the pyruvate dehydrogenase complex, citric acid cycle and electron transfer chain to provide energy for the liver

2. being stored in the liver after being converted to glycogen

3. being phosphorylated and exported into the bloodstream to maintain blood glucose levels.

4. being degraded into acetyl-CoA, and then converted to a fatty acid which can be used in the synthesis of lipids

5. entering the pentose phosphate pathway in order to produce NADPH (for lipid synthesis) and ribose-5-phosphate (precursor for nucleotide synthsis)

Five possible fates for fatty acids in the liver are:

1. being oxidised in B-oxidation, citric acid cycle and electron transfer chain to synthesise energy for the liver

2. after oxidation to produce acetyl-CoA, excess acetyl-CoA is converted to ketone bodies which can be used by other organs as fuel

3. after oxidation to produce acetyl-CoA, the acetyl-CoA is used to synthesise cholesterol (important in cell membranes, and the synthesis of steroid hormones and bile salts)

4. conversion to other types of lipids required by the liver

5. conversion to triacylglycerols and exported into the bloodstream as lipoproteins. The lipoproteins are then transported to the adipose tissue where the triacylglycerols are reformed and stored

Four possible fates for amino acids in the liver are:

1. use for synthesis of proteins required by the liver, and also blood plasma protein production

2. exported to other organs where they are used to synthesise tissue proteins

3. oxidation to provide energy, and the products are then fed into the citric acid cycle. Pyruvate and citric acid cycle intermediates (from glucogenic amino acids) can be used to synthesise glucose

4. use of acetyl-CoA derived from ketogenic amino acids to synthesise fatty acids (that are then used to form lipids for energy storage)

learning – the acquisition of new information or knowledge

memory – the retention and accessing of learned information

classes of memory

• • short term – phonological loop

    • • • • visuospatial sketchpad

• • long term – declarative (facts, places, events)

    • • • • perceptual

          • nondeclaritive (subconscious)

• • • relies on physical changes in neuronal circuits

    • reinforcement of particular synaptic pathways

    • changes in membrane receptors

    • hippocampal/medial temporal cortex involved in formation of long-term memories and the storage of recently formed long term memories

    • this may require the formation of new neurons

    • long term declarative memories are stored as synaptic circuits in the cerebral cortex

    • not all long term memories are declarative, as they can form without conscious acknowledgement

neuronal activity

• inferior temporal cortex important for facial recognition

• cells respond differently between different stimuli on training

Amnesias

• retrograde – previous memories removed after trauma

• anterograde – no memory after trauma

perceptual learning – practice in sensory tasks allows the person to perform finer discriminations, stored in primary sensory areas

visuomotor learning – compensating for visual disturbances (within cerebellum)

fear conditioning – amygdala coordinates behavioral, emotional and autonomic responses to sensory stimuli, learning association relies on this circuit

<!– /* Font Definitions */ @font-face {font-family:Wingdings; panose-1:5 0 0 0 0 0 0 0 0 0; mso-font-charset:2; mso-generic-font-family:auto; mso-font-pitch:variable; mso-font-signature:0 268435456 0 0 -2147483648 0;} @font-face {font-family:”Cambria Math”; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:1; mso-generic-font-family:roman; mso-font-format:other; mso-font-pitch:variable; mso-font-signature:0 0 0 0 0 0;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:”"; margin:0in; margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:12.0pt; font-family:”Times New Roman”,”serif”; mso-fareast-font-family:”Times New Roman”;} .MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-size:10.0pt; mso-ansi-font-size:10.0pt; mso-bidi-font-size:10.0pt;} @page Section1 {size:595.3pt 841.9pt; margin:44.95pt 28.3pt 1.0in 27.0pt; mso-header-margin:35.4pt; mso-footer-margin:35.4pt; mso-paper-source:0;} div.Section1 {page:Section1;} /* List Definitions */ @list l0 {mso-list-id:63376461; mso-list-type:hybrid; mso-list-template-ids:-1581198854 201916417 201916419 201916421 201916417 201916419 201916421 201916417 201916419 201916421;} @list l0:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} @list l1 {mso-list-id:209340533; mso-list-type:hybrid; mso-list-template-ids:122594592 201916417 201916419 201916421 201916417 201916419 201916421 201916417 201916419 201916421;} @list l1:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} @list l2 {mso-list-id:446775270; mso-list-type:hybrid; mso-list-template-ids:928784056 201916417 201916419 201916421 201916417 201916419 201916421 201916417 201916419 201916421;} @list l2:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} @list l3 {mso-list-id:1222060087; mso-list-type:hybrid; mso-list-template-ids:548674670 201916417 67698691 67698693 67698689 67698691 67698693 67698689 67698691 67698693;} @list l3:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} @list l4 {mso-list-id:1535926062; mso-list-type:hybrid; mso-list-template-ids:1153975298 201916417 201916419 201916421 201916417 201916419 201916421 201916417 201916419 201916421;} @list l4:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} @list l5 {mso-list-id:1646005561; mso-list-type:hybrid; mso-list-template-ids:-184809546 201916417 67698691 67698693 67698689 67698691 67698693 67698689 67698691 67698693;} @list l5:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} @list l6 {mso-list-id:1721977145; mso-list-type:hybrid; mso-list-template-ids:-1119349206 201916417 201916419 201916421 201916417 201916419 201916421 201916417 201916419 201916421;} @list l6:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:.75in; mso-level-number-position:left; margin-left:.75in; text-indent:-.25in; font-family:Symbol;} @list l7 {mso-list-id:1791048593; mso-list-type:hybrid; mso-list-template-ids:-372220112 201916431 201916441 201916443 201916431 201916441 201916443 201916431 201916441 201916443;} @list l7:level1 {mso-level-tab-stop:.5in; mso-level-number-position:left; text-indent:-.25in;} @list l7:level2 {mso-level-number-format:alpha-lower; mso-level-tab-stop:1.0in; mso-level-number-position:left; text-indent:-.25in;} @list l7:level3 {mso-level-number-format:roman-lower; mso-level-tab-stop:1.5in; mso-level-number-position:right; text-indent:-9.0pt;} @list l8 {mso-list-id:2022270059; mso-list-type:hybrid; mso-list-template-ids:1685643556 201916417 201916419 201916421 201916417 201916419 201916421 201916417 201916419 201916421;} @list l8:level1 {mso-level-number-format:bullet; mso-level-text:?; mso-level-tab-stop:1.5in; mso-level-number-position:left; margin-left:1.5in; text-indent:-.25in; font-family:Symbol;} ol {margin-bottom:0in;} ul {margin-bottom:0in;} –>

1. Describe cationic/anionic proteins and the concept of pI.

· Cationic proteins are positively charged because of their protonated side chain groups and NH3 N-terminus (present as NH4+). Anionic proteins are negatively charged because of their de-protonated side group and COOH C-terminus (present as COO-). At different pH’s, proteins can be positively or negatively charged. The isoelectric point is the pH at which a particular protein has no net charge because the overall number of negative charges equals the number of positive charges.

1. Describe the principles of:
   1. Ammonium sulphate precipitation. What was the range of Ammonium sulphate required for your protein? Was there a good yield of your protein?

· 50% concentration of ammonium sulphate was required to produce a good yield of protein (27.2%)

· Ammonium sulphate precipitation relies on the property of proteins to have variable ionic strength (according to the salt concentration) and therefore variable solubility. At low concentrations of salt, the solubility of the protein increases with the salt concentration. However, eventually a turning rate is reached, and as the salt concentration continues to rise the solubility of the protein begins to decrease. Ammonium sulphate precipitation exploits this to almost completely precipitate the protein out of solution when a sufficiently high ionic strength has been reached.

· Process: this process is carried out between 0 – 4*C to maximise protein stability. The solution of proteins is stirred continuously with small aliquots of crushed, solid ammonium sulphate being added in increments. Time is allowed between each increment to allow the ammonium sulphate to completely disperse and react with the required protein. The protein is then incubated at 0 – 4*C to allow the protein to precipitate and then subjected to a centrifuge to separate the precipitate. Each precipitate is then dissolved in fresh buffer to determine the total protein content and the enzyme activity. This is repeated until the percentage enzyme activity in precipitate is greater than 90%.

1. 1. Dialysis

· Is used to remove residual ammonium sulphate from the enzyme solution. The concentrated protein solution is placed in a dialysis bag that is semi-permeable to water and salt, but will not allow the protein to pass out. The bag is then placed in a large volume of buffer so that the salt ions diffuse out to equilibrate the solution. This process is repeated several times until most of the salt has diffused out of the bag and only the protein and the buffer solution are left.

1. 1. Ion-exchange chromatography. What is the principle of separation on the DEAE cellulose? Why was pH 8.0 chosen?

· Uses an insoluble matrix with charge groups covalently attached. Negatively charged exchangers bind positively charged ions (cations). They bind one kind of cation, but then when another, more highly charged cation is introduced, this new cation exchanges with the first.

· Proteins are charged molecules because several of the side chains are ionisable (such as the R-groups of lysine or glutamic acid, and the N-terminal amino acid and C-terminal carboxyl groups present in all amino acids). The charge on the protein depends on the number and type of ionisable amino acid side chain groups. Different proteins have different amino acid compositions and so will have different charges at different pH – allowing them to be fractionated. At the isoelectric point of the protein, it will not be attracted to the ion-exchange resin as there will be no net charge. The ion-exchanger used depends on the pH range of the protein. If the protein is most stable at pH values above its pI, an anion exchanger would be chosen. The pH chosen is crucial because it will determine the charge on the proteins being separated.

· DEAE cellulose contains an ionisable tertiary amine group, giving it a positive charge at pH 7, an anion exchanger. As the pH is lowered, COO- groups become protonated and lose their charge, decreasing their affinity for the resin. By slowly reducing the pH using a buffer pH gradient, the proteins are eluted as relatively clear fractions that can then be compared to the enzyme activity to further extract the protein.

· Process: the ion-exchange resin is poured into the column and then washed with buffer solution before the protein mixture is applied. Proteins that are oppositely charged to the resin will flow straight through the column and not bind. The proteins will be bound to different points along the column, depending on their differences in net charge.

· pH 8 is used because the value should be one pH unit above or below the pI of the protein to be separated to ensure adequate binding (and also so that there is movement from the origin). Also, as DEAE cellulose is an anionic exchanger, the starting pH must be sufficiently high to give a good spread of decreasing pH values (without becoming too acidic).

1. 1. Gel filtration

· Biological molecules can be separated due to the differences in shape and size, which lead them to have different abilities to penetrate porous matrixes. In protein purification, the matrix generally consists of porous beads of an inert, highly hydrated gel.

· This exercise used Sephadex G100 which can separate proteins of approximately 4000 – 150000 molecular weight. Ideally, the gel pore size should allow the desired protein to be partially excluded from the gel beads.

· Process: The gel beads are poured into a glass or plastic chromatography column, then they are allowed to settle by gravity. The column is then washed and brought to equilibrium with buffer solution before the protein (present in more buffer solution) is applied to the top of the column. As the proteins pass down the column they penetrate the pores of the gel matrix to different extents and so travel at different speeds. The larger proteins (that exceed the maximum size of the pores) will pass out first as they are unable to enter the beads. Other proteins will spend a proportion of their time within the gel beads, thereby moving more slowly through the column. The eluate is collected in a series of fractions according to size. The column can be calibrated with standard proteins of known molecular weight, thus giving approximate molecular weights (via graph) to the proteins present in the solution.

1. 1. Electrophoresis

· Relies on the fact that proteins have a net charge at any pH besides their pI. Proteins can be separated because every protein has a different net charge, and so will migrate at different rates towards the electrodes. The extent of molecular sieving relies on the gel pore size of the polyacrylamide gel. Bigger molecules move more slowly through the gel.

· The mixture of molecules to be separated is then placed in wells on a flat slab gel (0.75 – 1.5 mm thick) at a suitable distance from the electrodes so that proteins of different sizes separate out. After this, the positions of the separated protein bands are revealed by staining (Coomassie Blue or a silver stain).

· The main advantage of using electrophoresis is that many protein samples can be separated at once, using identical conditions so that the band patterns produced can be easily and relatively accurately compared.

1. 1. SDS-PAGE

· Uses almost identical principles as electrophoresis with a few minor differences.

· The protein mixture is first denatured by heating at 100*C for 2 – 5 minutes in the presence of SDS and thiol reagent. The mixture of molecules to be separated is then placed in wells on a flat slab gel (0.75 – 1.5 mm thick), which contains SDS and more electrode buffer, at a suitable distance from the electrodes so that proteins of different sizes separate out. After this, the positions of the separated protein bands are revealed by staining (Coomassie Blue or a silver stain).

· The charges of the polypeptides are basically negated by the negative charges provided by the bound detergent, so the SDS-polypeptide complexes have essentially the same overall charge. This means that the polypeptides separate strictly according to size, and hence the molecular weight can be estimated by creating a standard curve of polypeptide molecular weight verses distance migrated of each standard molecular weight marker and comparing the distance migrated by the unknown polypeptide.

1. 1. IEF (isoelectric focusing)

· Separates molecules by their charge characteristics. The protein mixture is subjected to an electric field in an inert support (usually either a vertical polyacrylamide rod gel or horizontal polyacrylamide rod gel) in which a stable pH gradient has been generated. The anode region is at a lower pH than the cathode, and it is ensured that the protein for separation has its isoelectric point within this range. A protein in a pH region less than its pI (therefore postively charged) will migrate towards the cathode. Proteins are separated by their pIs on the gel. It is important to have no molecular sieving effects (by using a large pore gel), so that separation is purely on the basis of charge.

· The stable pH gradient is formed by including a mixture of synthetic, aliphatic polyaminopolycarboxylic acids in the inert support. These are available commercially with either a wide pH range (3 – 10) or a narrow pH range (7-8).

· Unlike SDS-PAGE and electrophoresis, IEF does not provide information about the molecular weights of the separated polypeptides, but is able to provide an estimate of the pI of the polypeptide.

1. 1. 2D-PAGE

· Separates proteins on the basis of charge in one dimension and then by size in another dimension. The separation by charge is carried out by electrophoresis in a rod polyacrylamide gel. The rod is then placed on the top edge of the slab gel, where the proteins then migrate into the gel slab according to size. The gel is then stained so that the proteins appear as dots.

· Is used as a test of purity, but is not always accurate. Sometimes polypeptides will migrate as an aggregate because of interactions with each other. In order to separate out these proteins, additional reagents (such as urea) may need to be used during electrophoresis and sample preparation.

1. Do all the methods give identical values for the molecular mass of a particular protein? Compare the degree of accuracy that can be obtained with the molecular mass determined for SDS-PAGE with that obtained with mass spectrometry.

· The above methods do not give identical values for the molecular mass of a protein. In fact, techniques such as isoelectric focusing do not provide a means for estimating molecular mass (only pI). The molecular mass determined by mass spectrometry is relatively more accurate than SDS-page. SDS-PAGE only estimates the molecular mass by comparing the unknown protein’s distance travelled with a standard log curve created by plotting the values of know molecular mass samples. Mass spectrometry uses the mass to charge ratio of ions to determine the molecular mass of the unknown sample.

As most of you will have noticed, I’m no longer updating with any creative stuff. Currently, there is a lot of university things going on, such as those all-important, stupid exams. I hope you are all enjoying the excerpts from my learnings, and are willing to hang around until I put up a few more creative things. I’m still working on them, just very slowly.

I updated the ‘Accreditations’, ‘FAQ’ and ‘Thanks’ pages today, so if you wondered why they weren’t right, well, they are now.

Bear with me

~ Darkthorn

Describe the key physical features of the alpha-helix in terms of the number of backbone atoms, the number of residues in one turn and the hydrogen bond patterns.

• each hydrogen bond encloses a loop of the alpha-helix and contains 13 atoms, from a C = O group to the N – H group at the end
• one turn of the helix is made up of 10 atoms (3.6 residues)
• the hydrogen bonds that link one peptide bond to another are parallel to the axis of the helix and help stabilise the structure

Describe the key physical features of the beta-sheet in terms of the types of beta-sheets and forces that stabilise their structure. Where would each of the types of beta-sheets be likely to be found in a proteins structure and why?

<