Cyclobutane

A much studied model reaction in organic chemistry is the ring opening of cyclobutane to yield ethylene or the reverse, the combining of two ethylene molecules to form cyclobutane. ❋ Unknown (1999)

How does the reaction from the cyclobutane molecule to two ethylene molecules actually proceed? ❋ Unknown (1999)

You said "open chain structures" so I'm not considering ring structures like cyclobutane (C4H8). ❋ Unknown (2010)

CHS, contact hypersensitivity; CPD, cyclobutane pyrimidine dimer; ❋ Sebastian Majewski (2010)

Multiple mechanisms have evolved to repair damaged DNA, including the versatile nucleotide excision repair (NER) which is capable of removing a variety of bulky helix-distorting lesions, such as UV-induced cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts ❋ Xuefeng Chen Et Al. (2009)

Li S, Waters R (1996) Nucleotide level detection of cyclobutane pyrimidine dimers using oligonucleotides and magnetic beads to facilitate labelling of DNA fragments incised at the dimers and chemical sequencing reference ladders. ❋ Xuefeng Chen Et Al. (2009)

(A) DNA sequencing gels showing repair of UV-induced cyclobutane pyrimidine dimers (CPDs) in the transcribed strand of the ❋ Xuefeng Chen Et Al. (2009)

Because of the involvement of Polη in promoting error-free replication through cyclobutane pyrimidine dimers, its inactivation in humans causes the variant form of xeroderma pigmentosum, a genetic disorder characterized by a greatly enhanced predisposition to sun induced skin cancers ❋ Rodrigo Vasquez-Del Carpio Et Al. (2009)

27 This causes the hydrogen beyond this present threshold as the Iife form is moved into the lar density level will have to be - double bonds to break and create a where we have been kept by the next phase of the electromagnetic come less dense a n d grow more cyclobutane ring between t h e di - old solar paradigm of Power, spectrum. ❋ Czaragon (2009)