Two non-conventional analogues of ATP, 3'-deoxyadenosine-2'-triphosphate (3'-d-2'-ATP) and 2'-deoxyadenosine-3'-triphosphate (2'-d-3'-ATP), the syntheses of which are described, were examined as potential phosphate donors for the nucleoside kinases: 2'-deoxycytidine kinase (dCK), cytosolic thymidine kinase (TK1) and mitochondrial thymidine kinase (TK2). The reactions were monitored by means of a mixture of [γ-32P]ATP and cold analogue, andór with the use of 3H-labelled acceptors and cold donor. With dCK, using equimolar mixtures of ATP with each analogue, and dC as acceptor, phosphate transfer from 3'-d-2'-ATP and 2'-d-3'-ATP amounted to 34% and 14%, respectively. With each analogue used alone (each at concentration of 100 μM), phosphate transfer from 3'-d-2'-ATP was 55% that from ATP, and from 2'-d-3'-ATP 16%. With human TK2, and equimolar mixtures of [γ-32P]ATP with each of the analogues, and 1 μM dT as acceptor, there was no detectable transfer from either analogue. But, when each analogue was used alone, phosphate transfer attained 11% and 5%, respectively, that for ATP alone. With the low affinity form of human TK1, and dT as acceptor, only low phosphate transfer occurred with either analogue used alone. Both compounds exhibited Michaelis-Menten kinetics (with significantly lower Vmax than ATP), while ATP exhibited cooperative kinetics with all three kinases.
The importance of ciliates as a trophic link, which is defined as a fraction of the energy bound by primary producers that is transferred through the ciliate community, was assessed in the pelagic zones of shallow, eutrophic, and estuarine lakes. The study was conducted in Lake Gardno and Lake Łebsko located in northern Poland. Each of these lakes is characterized by very high mean annual ciliate biomasses of 115 μg C -1 (Lake Gardno, April 2006 – April 2007), 107 μg C L-1 (Lake Gardno, February 2007 – February 2008), 85 μg C L-1 (Lake Łebsko, April – November 2007), and 127 μg C L-1 (Lake Łebsko, April – September 2008). Ciliate production was estimated using allometric equations and was compared to primary production measured with the light-and-dark bottles method. Annual, depth-integrated ciliate secondary production corresponded to 9 and 11% (Lake Gardno, two consecutive years studied) and 12% (Lake Łebsko, the same value for two growing seasons studied) of primary production. These values exceed the majority of other estimates in the literature, which indicates the high importance of ciliates in such highly-productive, shallow lakes.