In our direct tissue investigations, we excluded methanol from the sample
preparation, and analyzed small samples of brain tissues from adult (n > 4) and juvenile (n = 2) lobsters. Representative spectra from an adult H. americanus brain ( Fig. 15E and F) and from a juvenile brain ( Fig. 15G and H) show complements of peptides similar to those detected by the Li group  and , including abundant signals from Val1-SIF and the orcokinin family peptides [Asn13], [His13], [Val13], Orc[1-12], SSEDMDRLGFGFN, FDAFTTGFGHN, and VYGPRDIANLY, all with mass measurement errors of less than 5 ppm. A careful examination of the mass range learn more where putative Orc[Ala11] should appear ( Fig. 15F and H) shows two peptides, TNWNKFQGSWamide (m/z 1266.60) and pQDLDHVFLRFamide (m/z 1271.65), which
had been detected in the previous work  and . While we did detect weak signals for Orc[1-11] in a few spectra, we did not detect signals for Orc[Ala11] in spectra for any of the brain tissues we examined. We also examined direct tissue spectra for the STG and CoG, two additional nervous system ganglia. Signals for putative Orc[Ala11] and Orc[1-11] were previously reported INNO-406 order in H. americanus STG tissues using direct tissue analyses  and , where acidified methanol was used to wash tissue samples and the tissue samples were co-crystallization with DHB in 50% methanol. In our direct tissue investigations of these ganglia, we once again excluded methanol from the sample preparation. A representative spectrum from an STG ( Fig. 15I and J) shows complements of peptides similar to those detected by the Li group  and , including an abundant signal from Val1-SIF. An examination of the mass range where putative Orc[Ala11] should appear ( Fig. 15I and J) shows three peptides, TNWNKFQGSWamide (m/z 1266.60), pQDLDHVFLRFamide (m/z 1271.65), and STNWSSLRSAWamide (m/z 1293.63), which have been detected in the previous work  and ; however, we did not detect signals for Orc[Ala11] in spectra
of any STG tissues we examined. We also failed to detect signals for Orc[Ala11] in the MALDI-FTMS spectra Pregnenolone for any CoGs ( Fig. 15K and L), where we have examined samples from over 20 individuals. For any study aspiring to characterize the endogenous components of a biological system, an underlying assumption is that the sampling and analysis approach will leave the sample in an unaltered state. Our results document a highly specific neuropeptide structural alteration, namely the combined truncation and C-terminal methylation of orcokinin family peptides, that occurs only when biological components of a crustacean tissue sample are present in an acidified methanolic extraction solvent. We used SORI-CID (product ion mass spectra from [M+H]+ and y5 ions) to identify an m/z 1270.57 peptide detected in H.