{"doi":"10.1002/mrm.29414","title":"Identification of <scp>l</scp>‐Tryptophan by down‐field <sup>1</sup>H MRS: A precursor for brain NAD<sup>+</sup> and serotonin syntheses","abstract":"PURPOSE: To explore the presence of new resonances beyond 9.4 ppm from the human brain, down-field proton MRS was performed in vivo in the human brain on 6 healthy volunteers at 7 T. METHODS: To maximize the SNR, a large voxel was placed within the brain to cover the maximal area in such a way that sinus cavities were avoided. A spectrally selective 90° E-BURP pulse with an excitation bandwidth of 2 ppm was used to probe the spectral chemical shift range between 9.1 and 10.5 ppm. The E-BURP pulse was integrated with PRESS spatial localization to obtain non-water-suppressed proton MR spectra from the desired spectral region. RESULTS: In the down-field proton MRS obtained from all of the volunteers scanned, we identified a new peak consistently resonating at 10.1 ppm. Protons associated with this resonance are in cross-relaxation with the bulk water, as demonstrated by the water saturation and deuterium exchange experiments. CONCLUSION: Based on the chemical shift, this new peak was identified as the indole (-NH) proton of l-tryptophan (l-TRP) and was further confirmed from phantom experiments on l-TRP. These promising preliminary results potentially pave the way to investigate the role of cerebral metabolism of l-TRP in healthy and disease conditions.","journal":"Magnetic Resonance in Medicine","year":2022,"id":269757,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":15,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.8899,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":275710,"name":"Mark A. Elliott","orcid":"0000-0003-4191-5509","position":1,"is_corresponding":false},{"id":891954,"name":"Anshuman Swain","orcid":"0000-0002-0257-8610","position":2,"is_corresponding":false},{"id":891953,"name":"Neil Wilson","orcid":"0009-0002-7766-2929","position":3,"is_corresponding":false},{"id":686831,"name":"Sophia Swago","orcid":"0000-0001-8334-4746","position":4,"is_corresponding":false},{"id":932994,"name":"Narayan Datt Soni","orcid":"0000-0001-6436-7299","position":5,"is_corresponding":false},{"id":329911,"name":"Walter R. Witschey","orcid":"0000-0003-1669-2120","position":6,"is_corresponding":false},{"id":227867,"name":"Ravinder Reddy","orcid":"0000-0003-4580-2392","position":7,"is_corresponding":false},{"id":469610,"name":"Ravi Prakash Reddy Nanga","orcid":"0000-0002-3644-5656","position":0,"is_corresponding":true}],"reference_count":34,"raw_metadata":null,"created_at":"2026-07-19T00:27:22.602796Z","pmid":"36005819","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}