Boron trifluoride etherate

Yeast samples were homogenized in chloroform/methanol (2:1, v/v) containing 0.01 % BHT as antioxidant, and total lipid extracted according to the Folch method (Folch et al., 1957) . Fatty acid methyl esters (FAME) were prepared by transesterification with boron trifluoride etherate (ca. 48 %, Acros Organics, NJ, USA) as described previously (Li et al., 2008; Xie et al., 2014) . FAME were purified by TLC, resuspended in hexane (Berry, 2004) , and separated using a gas chromatograph (GC2010-plus, Shimadzu, Japan) as described in detail previously (Li et al., 2010) . The activity of elongase was calculated as the proportion of substrate fatty acid converted to elongated FA products as follows: 100 × [individual product area / (all product areas + substrate area)] (Li et al., 2010) .

Lipid extraction and fatty acid analysis were performed as described previously (Li et al. 2005 (Li et al. , 2008)) . In brief, total lipid of liver and muscle tissues was extracted using chloroform and methanol in a 2:1 ratio, and fatty acid methyl esters were prepared by transesterifying the total lipid samples with boron trifluoride etherate (ca. 48 %, Acros Organics, NJ, USA). Fatty acid methyl esters were separated using a gas chromatograph (GC; GC-17A; Shimadzu, Kyoto, Japan) equipped with an auto sampler and a hydrogen-flame ionization detector. Individual fatty acids were identified by comparison with known commercial standards (Sigma, USA) and quantified using the CLASS-GC10 GC workstation (Shimadzu, Kyoto, Japan).

Cobalt(II) acetate, potassium graphite, sodium metal, mercury, and cobaltocene were purchased from Strem Chemicals. Acenaphthenequinone, hydroxylamine hydrochloride, boron trifluoride etherate, naphthalene, dibenzo-18-crown-6, 18-crown-6 and 12-crown-4 were purchased from Acros Organics and used as received. The ligand aqdH 2 was synthesized according to the published procedure of Satake et al. 52 All solvents used in the syntheses were purchased from Fisher Scientific, and dry solvents were obtained using a Pure Process Technology solvent purification system. Anhydrous DMF was purchased from Acros Organics and used without further purification for all the electrochemical studies.