. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SEXUAL PHEROMONES IN APLYSIA 169 Identification ofA-NTP as a potential attractant Previous studies (Nagle et a!., 1988b) have shown that the low molecular weight fraction III contains two pre- dominant peptide species, corresponding to A-NTP (N- terminal peptide encoded by the A gene) and B-NTP (N- terminal peptide encoded by the B gene). These peptides are each 13 residues in length, differing in sequence at only 3 positions, and have blocked amino termini (Fig. 4). Because amino acid compositional and microsequence analyse
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SEXUAL PHEROMONES IN APLYSIA 169 Identification ofA-NTP as a potential attractant Previous studies (Nagle et a!., 1988b) have shown that the low molecular weight fraction III contains two pre- dominant peptide species, corresponding to A-NTP (N- terminal peptide encoded by the A gene) and B-NTP (N- terminal peptide encoded by the B gene). These peptides are each 13 residues in length, differing in sequence at only 3 positions, and have blocked amino termini (Fig. 4). Because amino acid compositional and microsequence analyses indicate that A-NTP is present in significantly larger quantities than B-NTP (Nagle et a!.. 1988b), we decided to synthesize A-NTP for bioassay and future egg- cordon elution experiments. Peptide synthesis. A-NTP was synthesized at the Bio- molecular Synthesis Facility at the University of Texas Medical Branch and purified by CIS reversed-phase HPLC. The identity of the peptide was confirmed, and the amount of material quantified by amino acid com- positional analysis. Microsequence analyses (as described in Nagle et a/., 1988b) yielded no amino acid residues, confirming that the amino terminus was blocked. Bioassay. Three stimuli were examined in this series of experiments: (1) a nonlayer with nothing added to the ASW; (2) a nonlayer with a recently deposited conspecific egg cordon (laid by another animal following injection of atrial gland extract; deposition completed within the pre- ceding 30 min; mean volume, ml); and (3) a nonlayer with 100 ng of synthetic A-NTP (60% of the amount of A-NTP and B-NTP in one gland; Nagle et al., I988b). Animals. Animals were selected from a pool of 183. Results. Because of the larger population of animals used in these experiments, directional bias and chance levels of attraction were reassessed. Four of 15 animals () travelled to the left when there was no stimulus in either arm, three of 15 (20%) travelled to the right, and eig
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