Separating the two Strands of a DNA double Helix Odvajanje dva smjera DNA dvokrevetne Helix

While the ratios of G to C and A to T in an organism's DNA are fixed, the GC content (percentage of G +C) can vary considerably from one DNA to another.When a DNA solution is heated enough, the non-covalent forces that hold the two strands together weaken and finally break.When this happens, the two strands come apart in a process known as DNA denaturation, or DNA melting.The temperature at which the DNA strands are half denatured is called the melting temperature, or Tm. Iako je Pokazivači u C i G u T A da u organizmu's DNA su fiksne, GC sadržaj (postotak G + C) može značajno varirati od jedne do another.When DNA DNA rješenje je dovoljno zagrijane, non-covalent snage da se držite dva smjera zajedno oslabiti i na kraju break.When se to dogodi, dva smjera dolazi osim u proces poznat i kao DNA denaturation, ili DNA melting.The temperatura na kojoj se DNA strukturi su polovina denaturirani se naziva melting temperature, ili Tm . The amount of strand separation, or melting, is measured by the absorbance of the DNA solution at 260nm.Nucleic acids absorb light at this wavelength because of the electronic structure in their bases, but when two strands of DNA come together, the close proximity of the bases in the two strands quenches some of this absorbance.When the two strands separate, this quenching disappears and the absorbance rises 30%-40%.This is called hyperchromic shift. Iznos nasukavanje razdvajanja, ili melting, se mjeri u absorbance of DNA rješenje na 260nm.Nucleic kiselina apsorbiraju svjetlo na ovu valna duljina, jer je elektronska struktura u njihove baze, ali kada se dva smjera DNA dolaze zajedno, neposrednoj blizini podnožja u dva smjera quenches neke od ove absorbance.When dva odvojena smjera, ovo gašenje nestaje i absorbance uzdiže se 30% -40%. To se zove hyperchromic smjeni.
The GC content of DNA has a significant effect on its Tm.The higher a DNA's GC content, the higher its Tm.Why should this be?One of the forces holding the two strands of DNA together is hydrogen bonding.Also GC pairs form three hydrogen bonds, whereas AT pairs have only two.It stands to reason, then that two strands of DNA rich in G and C will hold to each other more tightly than those of AT-rich DNA. The GC sadržaj DNA ima značajan utjecaj na njegove Tm.The veći DNA's GC sadržaja, veći svojim Tm.Why ovo bi trebalo biti? Jedan od snage drži dva smjera DNA je zajedno vodik bonding.Also GC parove obliku tri vodikove veze, dok je AT parove imaju samo two.It stoji na razlog, zatim da su dva smjera DNA bogata u G i C održat će se međusobno više nego dobro one AT-bogata DNA.
Heating is not the only way to denature DNA.Organic solvents such as dimethyl sulfoxide and formamide, or high pH, disrupt the hydrogen bonding between DNA strands and promote denaturation.Lowering the salt concentration of the DNA solution also aids denaturation by removing the ions that shield the negative charges on the two strands from one another.At low ionic strength, the mutually repulsive forces of the negative charges are strong enough to denature the DNA ar a relatively low temperature. Grijanje nije jedini način da denaturirati DNA.Organic otapala kao što su dimethyl sulfoxide i formamide, ili visok pH, ometalo vodikovih veza između DNA strukturi i promicanje denaturation.Lowering je koncentracija soli od DNA rješenje i pomagala denaturation uklanjanjem iona koji štit negativne optužbi na jedan od dva smjera another.At low ionic snagu, obostrano odbojan snage negativne troškove dovoljno su jaki da denaturirati DNA na relativno niska temperatura.