Pyrolysis-GC×GC-TOFMS as a tool for distinguishing the macromolecular structure of nitrogen-bearing animal biopolymers in fossil tissues

Umamaheswaran, Raman; Dutta, Suryendu; Singh, Himanshu; Kumar, Sumit

doi:10.1016/j.jaap.2021.105362

Cited by 4 publications

(3 citation statements)

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“…It is also worth noting that the distribution of 2,5‐DKPs obtained from the Pliocene scale, which showed cyclo (Pro‐Gly) and cyclo (Pro‐Ala) in greater abundance, resemble more closely those of the modern fish vertebra reported by Dutta et al (2020), rather than the early Eocene vertebra from the same study that displayed cyclo (Pro‐Pro) and cyclo (Pyr‐Pyr) as the two DKPs in greatest abundance. These were also, incidentally, the only two DKPs observed in the Eocene mammal bone from Umamaheswaran, Dutta, Singh, et al (2022). This suggests that the level of diagenetic alteration in the Pliocene scale is minimal.…”

Section: Discussionmentioning

confidence: 82%

“…It is also important to note that the formation of DKPs during pyrolysis of peptides displays a bias towards proline‐derived ones, presumably due to their ease of formation from Pro, and their relative stability (Fabbri et al, 2012). Hence, while diketodipyrrole has been suggested as a characteristic pyrolysis product of collagen (Stankiewicz, Hutchins, et al, 1997; Gupta, 2013; Gupta et al, 2008), reported in high abundance in archaeological collagen samples, particularly bone collagen (Adamiano et al, 2013: Kaal et al, 2016; Orsini et al, 2017) and in fossil bone and egg shell samples (Dhiman et al, 2021; Dutta et al, 2020; Umamaheswaran, Dutta, Singh, et al, 2022), based on our results we would urge caution in interpreting this signal in isolation as evidence for collagen or collagenous moieties in paleontological specimens, and rather advocate for its use as a potential indicator for the preservation of proteinaceous moieties, or potentially even diffuse amino acids. We suggest that any arguments proposed in favor of collagen preservation in fossil samples be based on the presence of a suite of DKPs, especially cyclo (Pro‐Gly) in high relative abundance, or DKPs that are unambiguously derived from hydroxyproline such as cyclo (Pro‐Hyp), as opposed to exclusively the presence of diketodipyrrole.…”

Section: Discussionmentioning

confidence: 99%

“…Helium was used as carrier gas at a constant flow rate of 1.5 ml min −1 . The GC × GC‐TOFMS method was modified after Umamaheswaran, Dutta, et al (2022) and Umamaheswaran, Dutta, Khan, et al (2022) The primary oven was kept at 40°C (held for 2 min), ramped to 180°C at 10°C min −1 , again ramped at 5°C min −1 to 270°C, and subsequently raised to 295°C at 3°C min −1 (held for 10 min). The secondary oven temperature was programmed at a +10°C offset to the primary oven temperature.…”

Section: Methodsmentioning

confidence: 99%

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The diagenetic fate of collagen as revealed by analytical pyrolysis of fossil fish scales from deep time

et al. 2022

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The mechanism of protein degradation has remained a topic of debate (specifically concerning their preservation in deep time), which has recently been invigorated due to multiple published reports of preservation ranging from Miocene to the Triassic that potentially challenge the convention that protein preservation beyond the Cenozoic is extremely uncommon or is expected to be absent altogether, and thus have attracted skepticism. In this paper, we analyze fossil fish scales from the Cretaceous, Jurassic, and Triassic using comprehensive pyrolysis gas chromatography coupled with time‐of‐flight mass spectrometry and compare the pyrolytic products so obtained with a well‐preserved fish scale from Late Pliocene, in an attempt to better understand the effects of diagenesis on protein degradation at the molecular level through deep time. We find that the Pliocene fish scale displays a large number of N‐bearing pyrolytic products, including abundant substituted cyclic 2,5‐diketopiperazines (2,5‐DKPs) which are diagnostic products of peptide and amino acid pyrolysis. We identify N‐bearing compounds in the Mesozoic fish scales—however, among the 2,5‐DKPs that were identified in the Pliocene scale, only diketodipyrrole (or cyclo (Pyr‐Pyr)) is present in the Mesozoic scales. We discuss the implications of N‐bearing pyrolytic products with emphasis on 2,5‐DKPs in geological samples and conclude that the discrepancy in abundance and variety of N‐bearing products between Pliocene and Mesozoic scales indicates that the protein component in the latter has been extensively diagenetically altered, while a suite of DKPs such as in the former would imply stronger evidence to indicate preservation of protein. We conclude that analytical pyrolysis is an effective tool for detecting preservation of intact proteins, as well as for providing insights into their degradation mechanisms, and can potentially be utilized to assign proteinaceous origin to a fossil sample of unknown affinity.

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Section: Discussionmentioning

confidence: 82%