{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,1]],"date-time":"2026-05-01T18:32:27Z","timestamp":1777660347865,"version":"3.51.4"},"reference-count":19,"publisher":"MDPI AG","issue":"19","license":[{"start":{"date-parts":[[2021,9,22]],"date-time":"2021-09-22T00:00:00Z","timestamp":1632268800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Materials"],"abstract":"<jats:p>We developed non-toxic, harmless adhesives composed of all-natural and renewable resources, of which one was composed of tannin and gelatin, which unfortunately was lacking water resistance, and the other of tannin and \u03b5-poly-l-lysine. In this study, we analyzed the chemical structures of these adhesives by two-dimensional nuclear magnetic resonance (2D-NMR) to explain the difference in water-resistance of the two glues. The results showed that only one proton was left in the benzene ring of tannin after mixing. This suggests that the amino group of the protein was directly attached to the benzene ring by a Michael addition-type reaction, and not to the hydroxyl group. In addition, the heteronuclear multiple bond correlation spectrum of the tannin-poly-l-lysine compound indicated that the hydroxyl groups of the tannin oxidized, suggesting the improvement of its water resistance.<\/jats:p>","DOI":"10.3390\/ma14195479","type":"journal-article","created":{"date-parts":[[2021,9,26]],"date-time":"2021-09-26T22:24:13Z","timestamp":1632695053000},"page":"5479","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":6,"title":["Analysis of the Structural Aspects of Tannin-Based Adhesives by 2D-NMR"],"prefix":"10.3390","volume":"14","author":[{"given":"Sachikazu","family":"Omura","sequence":"first","affiliation":[{"name":"Institute of Natural Drug-Leads, Kanagawa University, Hiratsuka 259-1293, Kanagawa, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Yoshinori","family":"Kawazoe","sequence":"additional","affiliation":[{"name":"Center for Education and Research in Agricultural Innovation, Faculty of Agriculture, Saga University, Karatsu 847-0021, Saga, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Daisuke","family":"Uemura","sequence":"additional","affiliation":[{"name":"Institute of Natural Drug-Leads, Kanagawa University, Hiratsuka 259-1293, Kanagawa, Japan"},{"name":"Department of Chemistry, Kanagawa University, Hiratsuka 259-1293, Kanagawa, Japan"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2021,9,22]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"35","DOI":"10.1016\/j.ijadhadh.2016.12.009","article-title":"Development of a novel adhesive composed of all-natural components","volume":"74","author":"Omura","year":"2017","journal-title":"Int. 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