As a base for human transcriptome and functional genomics, we created the "full-length long Japan" (FLJ) collection of sequenced human cDNAs. We determined the entire sequence of 21,243 selected clones and found that 14,490 cDNAs (10,897 clusters) were unique to the FLJ collection. About half of them (5,416) seemed to be protein-coding. Of those, 1,999 clusters had not been predicted by computational methods. The distribution of GC content of nonpredicted cDNAs had a peak at ∼58% compared with a peak at ∼42%for predicted cDNAs. Thus, there seems to be a slight bias against GC-rich transcripts in current gene prediction procedures. The rest of the cDNAs unique to the FLJ collection (5,481) contained no obvious open reading frames (ORFs) and thus are candidate noncoding RNAs. About one-fourth of them (1,378) showed a clear pattern of splicing. The distribution of GC content of noncoding cDNAs was narrow and had a peak at ∼42%, relatively low compared with that of protein-coding cDNAs.

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Recently, it has become clear that single, long duplex DNAs exhibit a large discrete transition between elongated coil and compacted globule states. To obtain further insight into this phenomenon, in the present study we observed individual DNA chains in an aqueous environment by fluorescence microscopy. The long-axis lengths of individual T4DNA (166 kbp) were calibrated to obtain a size distribution. The main purpose of the present study was to determine the effect of the valence of cations on the coil−globule transition. We used the following multivalent cations to induce the compaction of long DNA chains:  1,3-diaminopropane (bivalent), spermidine (trivalent), and spermine (tetravalent). Our results showed that the collapse of isolated DNA chains induced by either bivalent or multivalent cations is discrete. The critical concentration of cation for inducing the transition was lowest for the tetravalent cation and highest for the bivalent cation. We also compare the properties of the transition observed experimentally with a theoretical calculation including the effects on condensation of multivalent cations and ion-exchange reaction.

From the study of single molecular observation of individual DNA chains by use of fluorescence microscopy, it has become clear that the transition between elongated coil state and compacted globule state is highly discrete on the level of individual chains. On the other hand, the transition appears continuous on the level of the ensemble of DNAs. We report the experimental evidence on this unique property of the DNA chain, using T4 DNA, 166 kilo base pairs (kbp), with the addition of Co(NH3)3+6. Theoretical consideration has been performed on the bimodality in the free energy of single DNA chains, indicating that the character of the coil‐globule transition changes largely depending on the valency of the coexistence cationic species.