Third-generation sequencers

A different technology used by third-generation sequencers is the one developed by companies such as Halcyon or ZS Genetics that uses a rapid-scan tunneling electron microscope to read the DNA chain directly (44). DNA bases have to be labeled with heavy atoms to make them visible under the electron microscopy. Each nucleotide is tagged with a characteristic heavy label so that they can be distinguished in the transmission electron micrograph. 

Ozsolak, R, Third-generation sequencing techniques and applications to drug discovery. Expert Opin. Drug Discovery, 2012. 7(3) 231-243. 

Further examinations have been done in the biodegradation ecotoxicity sequence rest (BEST). In this test a realistic diluted effluent of the modified OECD confirmatory test (DIN 38412, part 26) is tested continually on daphnia reproduction over three generations. It can be said that the effluents of an OECD confirmatory plant (feed 10 mg/L LAS), containing nondegraded surfactants and catabolites, have no negative effect on the juvenile and adult daphnia even in the third generation and do not influence their reproduction [296]. 

The bromosilane obtained by reaction of the phenylsiloxane 1 with bromine in the presence of triethylamine or sodium siloxide led Kakimoto et al. to the siloxane core building block 4. It contains three phenylsilane-terminated disilox-ane branching units, which should minimise steric hindrance on construction of subsequent generations. A sequence of bromination, amination, and alcoholysis ultimately leads to the third-generation polysiloxane 5 (Fig. 4.50) [99]. 

NaH to give the advanced enone 137 (Z E = 10 1). A further four steps were then required to complete the third-generation synthesis, beginning with C19 carbamate installation, followed by K-Selectride reduction to introduce the requisite (75)-stere-ocentre. Finally, global deprotection with concomitant S-lactonisation gave disco-dermolide (1) in 11.1% overall yield over 21 steps (longest linear sequence). 

Figure 2.25 shows a typical sequence of operations used to observe third-generation ions. 

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