Marwa Shinwari

• Polyamides


  Polymers where the repeating units are held together by amide links
• Amide group


  Has the formula -CONH2
• Amide link


  Has the structure -CONH-
• Amide groups are also called peptide groups and are found in proteins
• Nylon


  Polyamide where the repeating units contain chains of carbon atoms
• Nylon-6,6


  Made from two monomers each containing 6 carbon atoms - hexanedioic acid and 1,6-diaminohexane
• Formation of nylon-6,6


  Amine and acid groups combine with loss of water (condensation polymerisation)
• Nylon-6


  Made from a single monomer called caprolactam which already contains an amide link
• Kevlar


  Polyamide similar to nylon-6,6 but with benzene rings instead of carbon chains
• Monomers for Kevlar


  Benzene-1,4-dicarboxylic acid and 1,4-diaminobenzene
• Industrial production of nylon-6,6

  1. Hexanedioic acid and 1,6-diaminohexane react to form a salt, then heated to 350°C to produce nylon-6,6

  2. Monomers made from cyclohexane
• Lab production of nylon-6,6

  Use hexanedioyl dichloride instead of hexanedioic acid, reaction with 1,6-diaminohexane releases HCl instead of H2O
• Nylon rope trick


  Carefully float solutions of hexanedioyl dichloride and 1,6-diaminohexane, nylon-6,6 forms at the boundary and can be pulled out
• Hydrolysis of polyamides


  • Easily hydrolysed by strong acids, more resistant to alkaline hydrolysis
  • Hydrolysis faster at higher temperatures
  • Hydrolysis by water alone is very slow
• Kevlar is more resistant to hydrolysis than nylon
• Hydrolysis of nylon


  Breaks amide linkages, producing original monomers and destroying the fibres
• Uses of nylon


  • Textiles, tyre cords, ropes, machine parts
• Uses of Kevlar


  • Bulletproof vests, boat construction, mountaineering ropes, lightweight skis and racquets
• Probes


  An important tool in the location and identification of genes used in recombinant DNA technology
• Genetic probe


  A single strand of DNA that contains the known complementary base pairs of the gene and a marker for identification
• Types of probes


  • DNA probes
  • RNA probes
• Marker on a probe

  May be radioactive or have fluorescence
• Hybridisation


  The process where a probe binds to a complementary DNA or RNA sequence
• Applications of probes


  • Identification of individual's response to certain drugs or their risk of developing diseases
  • Identification of nucleotide sequence at point mutation to track inheritance of disease-associated with genetic variants within families
• RNA probes


  Produced using RNA polymerase and nucleotides that are either radioactively labelled or labelled using fluorophores
• Applications of RNA probes

  • Southern / Northern blot hybridisation to detect the mRNA of interest
  • Used in forensic science to identify suspects that match the crime scene
• Alkaline phosphatase


  Removes 5' phosphate groups from DNA (and RNA), most active at alkaline pH
• Uses of alkaline phosphatase

  • In labelling - removing 5' phosphates from fragments of DNA prior to labelling with radioactive phosphate
  • In preventing cut fragments from immediately recombining when inserting new fragments of DNA into a DNA molecule
• Alkaline phosphatase is a DNA modifying enzyme that either adds or removes specific phosphate group at 5' terminus of double stranded DNA (dsDNA) or single stranded DNA (ssDNA) or RNA
• When removing the phosphates from the ends of DNA fragments (via alkaline phosphatase activity) the polynucleotide kinase enzyme is more effective in phosphorylating DNA
• Southern blotting


  A technique that uses DNA probes for the identification and quantification of specific DNA sequences in large, complex samples of DNA
• Northern blotting


  A technique that uses RNA probes for the identification and quantification of specific RNA sequences in large, complex samples of RNA
• Promoter


  A region of DNA where transcription of a gene is initiated, controls when and where a gene of interest is expressed
• Promoter region


  • About 100-1000 base pairs long, adjacent and typically upstream (5') of the sense or coding strand of the transcribed gene, contains the RNA polymerase binding site, TATA box, and transcription start site
• Oligonucleotide synthesis


  The artificial chemical synthesis of relatively short fragments of nucleic acids with defined chemical structure (sequences)
• Polymerase chain reaction (PCR)


  A process used to amplify (increase) the number of DNA molecules within a sample
• Steps of PCR


  1. Isolate target DNA

  2. Mix with DNA polymerase and oligonucleotide primers

  3. Heat to 95°C to separate DNA strands

  4. Cool to 53°C and primers anneal to DNA strands

  5. DNA polymerase extends primers by adding nucleotides
• Polymerase Chain Reaction (PCR)

  1. Isolate target DNA

  2. Mix with DNA polymerase and primers

  3. Heat to 95°C to separate DNA strands

  4. Cool to 53°C to allow primers to bind

  5. Increase temperature to 73°C for DNA polymerase to extend new strands

  6. Repeat cycle to exponentially amplify target DNA
• Primers


  Short, synthetic DNA fragments that are complementary to DNA sequences and bind to the ends of the separated DNA strands
• DNA Polymerase


  Enzyme that binds to primers and adds nucleotides to form new complementary DNA strands