BIOL240 Lecture Notes - Lecture 21: Antibiotics, Microorganism, Lipid A

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Freezing: can damage cells by forming ice crystals, can stop biochemical reactions, good for long term preservation, can keep species over years; avoid temps of +5 to -5c because water crystals form which damages membranes. So to avoid this, pass through cold quickly and use glycerol. Electromagnetic radiation: uv radiation of 260 280 nm wavelengths, can damage dna by forming thymine dimers. This happens when you have 2 thymine bases next to each other on the strand. Uv light causes a covalent link to form between them. Polymerases recognize the dimer as one thymine which leads to frameshift. This leads to cell death: this is not used for sterilization; just control over the microbial growth, exploited to control microbial growth on non- living surfaces and in water. Radiation (eg. co 60: protein and dna damage, double strand breaks, forms stray e-, hydroxide ions, hydride radicals which are the cause for dna damage, higher energy (measured in grays), better penetrations.

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