Prevalent intrinsic emission from nonaromatic amino acids and poly(amino acids)

More info
  • ReceivedJul 22, 2017
  • AcceptedJul 23, 2017
  • PublishedSep 6, 2017


Nonaromatic amino acids are generally believed to be nonemissive, owing to their lack of apparently remarkable conjugation within individual molecules. Here we report the intrinsic visible emission of nonaromatic amino acids and poly(amino acids) in concentrated solutions and solid powders. This unique and widespread luminescent characteristic can be well rationalized by the clustering-triggered emission (CTE) mechanism, namely the clustering of nonconventional chromophores (i.e. amino, carbonyl, and hydroxyl) and subsequent electron cloud overlap with simultaneous conformation rigidification. Such CTE mechanism is further supported by the single crystal structure analysis, from which 3D through space electronic communications are uncovered. Besides prompt fluorescence, room temperature phosphorescence (RTP) is also detected from the solids. Moreover, persistent RTP is observed in the powders of exampled poly(amino acids) of ε-poly-L-lysine (ɛ-PLL) after ceasing UV irradiation. These results not only illustrate the feasibility of employing the building blocks of nonaromatic amino acids in the exploration of new luminescent biomolecules, but also provide significant implications for the emissions of peptides and proteins at aggregated or crystalline states. Meanwhile, they may also shed lights on further understanding of autofluorescence from biological systems.

Funded by

National Natural Science Foundation of China(51473092)

Shanghai Rising-Star Program(15QA1402500)


This work was supported by the National Natural Science Foundation of China (51473092), and the Shanghai Rising-Star Program (15QA1402500). The authors appreciate Ms Xiaoli Bao and Ms Lingling Li at the Instrumental Analysis Center of Shanghai Jiao Tong University for the single-crystal structure determination of L-Ile.

Interest statement

The authors declare that they have no conflict of interest.


The supporting information is available online at http://chem.scichina.com and http://link.springer.com/journal/11426. The supporting materials are published as submitted, without typesetting or editing. The responsibility for scientific accuracy and content remains entirely with the authors.


[1] Saviotti ML, Galley WC. Proc Natl Acad Sci USA, 1974, 71: 4154-4158 CrossRef Google Scholar

[2] Vanderkooi JM, Calhoun DB, Englander SW. Science, 1987, 236: 568-569 CrossRef ADS Google Scholar

[3] Papp S, Vanderkooi JM. Photochem Photobiol, 1989, 49: 775-784 CrossRef Google Scholar

[4] Lakowicz JR. Principles of Fluorescence Spectroscopy. 3rd Ed. New York: Springer, 2006. Google Scholar

[5] Maki AH, Zuclich J. Top Curr Chem, 1975, 54: 115−163. Google Scholar

[6] Homchaudhuri L, Swaminathan R. Chem Lett, 2001, 30: 844-845 CrossRef Google Scholar

[7] Homchaudhuri L, Swaminathan R. Bull Chem Soc Jpn, 2004, 77: 765-769 CrossRef Google Scholar

[8] Shukla A, Mukherjee S, Sharma S, Agrawal V, Radha Kishan KV, Guptasarma P. Archives Biochem Biophys, 2004, 428: 144-153 CrossRef PubMed Google Scholar

[9] Chan FTS, Kaminski Schierle GS, Kumita JR, Bertoncini CW, Dobson CM, Kaminski CF. Analyst, 2013, 138: 2156-2162 CrossRef PubMed ADS Google Scholar

[10] Pinotsi D, Grisanti L, Mahou P, Gebauer R, Kaminski CF, Hassanali A, Kaminski Schierle GS. J Am Chem Soc, 2016, 138: 3046-3057 CrossRef PubMed Google Scholar

[11] Sharpe S, Simonetti K, Yau J, Walsh P. Biomacromolecules, 2011, 12: 1546-1555 CrossRef PubMed Google Scholar

[12] Del Mercato LL, Pompa PP, Maruccio G, Della Torre A, Sabella S, Tamburro AM, Cingolani R, Rinaldi R. Proc Natl Acad Sci USA, 2007, 104: 18019-18024 CrossRef PubMed ADS Google Scholar

[13] Pinotsi D, Buell AK, Dobson CM, Kaminski Schierle GS, Kaminski CF. ChemBioChem, 2013, 14: 846-850 CrossRef PubMed Google Scholar

[14] Ye R, Liu Y, Zhang H, Su H, Zhang Y, Xu L, Hu R, Kwok RTK, Wong KS, Lam JWY, Goddard WA, Tang BZ. Polym Chem, 2017, 8: 1722-1727 CrossRef Google Scholar

[15] Gong YY, Tan YQ, Mei J, Zhang YR, Yuan WZ, Zhang YM, Sun JZ, Tang BZ. Sci China Chem, 2013, 56: 1178-1182 CrossRef Google Scholar

[16] Zhou Q, Cao B, Zhu C, Xu S, Gong Y, Yuan WZ, Zhang Y. Small, 2016, 12: 6586−6592. Google Scholar

[17] Yuan WZ, Zhang Y. J Polym Sci Part A-Polym Chem, 2017, 55: 560-574 CrossRef ADS Google Scholar

[18] Lee WI, Bae Y, Bard AJ. J Am Chem Soc, 2004, 126: 8358-8359 CrossRef PubMed Google Scholar

[19] Wang D, Imae T. J Am Chem Soc, 2004, 126: 13204-13205 CrossRef PubMed Google Scholar

[20] Zhu S, Song Y, Shao J, Zhao X, Yang B. Angew Chem Int Ed, 2015, 54: 14626-14637 CrossRef PubMed Google Scholar

[21] Sun M, Hong CY, Pan CY. J Am Chem Soc, 2012, 134: 20581-20584 CrossRef PubMed Google Scholar

[22] Pucci A, Rausa R, Ciardelli F. Macromol Chem Phys, 2008, 209: 900-906 CrossRef Google Scholar

[23] Zhao E, Lam JWY, Meng L, Hong Y, Deng H, Bai G, Huang X, Hao J, Tang BZ. Macromolecules, 2015, 48: 64-71 CrossRef ADS Google Scholar

[24] Miao X, Liu T, Zhang C, Geng X, Meng Y, Li X. Phys Chem Chem Phys, 2016, 18: 4295-4299 CrossRef PubMed ADS Google Scholar

[25] Yu W, Wu Y, Chen J, Duan X, Jiang XF, Qiu X, Li Y. RSC Adv, 2016, 6: 51257-51263 CrossRef Google Scholar

[26] Niu S, Yan H, Chen Z, Li S, Xu P, Zhi X. Polym Chem, 2016, 7: 3747-3755 CrossRef Google Scholar

[27] All experiments were conducted at room temperature unless specified. Though some concentrated nonaromatic amino acids are nonemissive at room temperature, they do become emissive when frozen by liquid nitrogen (Figure S1). And some relatively weakly emissive crystals (i.e. L-Leu, D-Leu, and D-Met) get more emissive upon cooling to 77 K (Figure S7). Google Scholar

[28] Mei J, Leung NLC, Kwok RTK, Lam JWY, Tang BZ. Chem Rev, 2015, 115: 11718-11940 CrossRef PubMed Google Scholar

[29] Fan Z, Sun L, Huang Y, Wang Y, Zhang M. Nat Nanotech, 2016, 11: 388-394 CrossRef PubMed ADS Google Scholar

[30] Tested with the detector at nanosecond scale. Google Scholar

[31] For the PerkinElmer LS 55 fluorescence spectrometer, with a td≥0.1 ms, all prompt fluorescence signals with nanoscale lifetime can be excluded. Google Scholar

[32] Yuan WZ, Shen XY, Zhao H, Lam JWY, Tang L, Lu P, Wang C, Liu Y, Wang Z, Zheng Q, Sun JZ, Ma Y, Tang BZ. J Phys Chem C, 2010, 114: 6090-6099 CrossRef Google Scholar

[33] Wang CR, Gong YY, Yuan WZ, Zhang YM. Chin Chem Lett, 2016, 27: 1184-1192 CrossRef Google Scholar

[34] Hirata S, Totani K, Zhang J, Yamashita T, Kaji H, Marder SR, Watanabe T, Adachi C. Adv Funct Mater, 2013, 23: 3386-3397 CrossRef Google Scholar

[35] An Z, Zheng C, Tao Y, Chen R, Shi H, Chen T, Wang Z, Li H, Deng R, Liu X, Huang W. Nat Mater, 2015, 14: 685-690 CrossRef PubMed ADS Google Scholar

[36] Yang Z, Mao Z, Zhang X, Ou D, Mu Y, Zhang Y, Zhao C, Liu S, Chi Z, Xu J, Wu YC, Lu PY, Lien A, Bryce MR. Angew Chem Int Ed, 2016, 55: 2181-2185 CrossRef PubMed Google Scholar

[37] Gong Y, Chen G, Peng Q, Yuan WZ, Xie Y, Li S, Zhang Y, Tang BZ. Adv Mater, 2015, 27: 6195-6201 CrossRef PubMed Google Scholar

[38] Li C, Tang X, Zhang L, Li C, Liu Z, Bo Z, Dong YQ, Tian YH, Dong Y, Tang BZ. Adv Opt Mater, 2015, 3: 1184-1190 CrossRef Google Scholar

[39] Xu S, Chen R, Zheng C, Huang W. Adv Mater, 2016, 28: 9920-9940 CrossRef PubMed Google Scholar

[40] Xie Y, Ge Y, Peng Q, Li C, Li Q, Li Z. Adv Mater, 2017, 29: 1606829 CrossRef PubMed Google Scholar

[41] Zhao W, He Z, Lam JWY, Peng Q, Ma H, Shuai Z, Bai G, Hao J, Tang BZ. Chem, 2016, 1: 592-602 CrossRef Google Scholar

[42] Wei J, Liang B, Duan R, Cheng Z, Li C, Zhou T, Yi Y, Wang Y. Angew Chem Int Ed, 2016, 55: 15589-15593 CrossRef PubMed Google Scholar

[43] Yan D. Sci China Chem, 2017, 60: 163-164 CrossRef Google Scholar

[44] He G, Torres Delgado W, Schatz DJ, Merten C, Mohammadpour A, Mayr L, Ferguson MJ, McDonald R, Brown A, Shankar K, Rivard E. Angew Chem Int Ed, 2014, 53: 4587-4591 CrossRef PubMed Google Scholar

[45] Chen H, Yao X, Ma X, Tian H. Adv Opt Mater, 2016, 4: 1397-1401 CrossRef Google Scholar

[46] Shimizu M, Kimura A, Sakaguchi H. Eur J Org Chem, 2016, 2016: 467-473 CrossRef Google Scholar

[47] Chen X, Xu C, Wang T, Zhou C, Du J, Wang Z, Xu H, Xie T, Bi G, Jiang J, Zhang X, Demas JN, Trindle CO, Luo Y, Zhang G. Angew Chem Int Ed, 2016, 55: 9872-9876 CrossRef PubMed Google Scholar

[48] Boldyreva EV, Kolesnik EN, Drebushchak TN, Ahsbahs H, Beukes JA, Weber H-P. Z Kristallogr, 2005, 220: 58−65. Google Scholar

[49] CCDC 1542778 contains the supplementary crystallographic data for L-Ile. These data can be obtained free of charge from The Cambridge Crystallographic Data Centre via www.ccdc.cam.ac.uk/data_request/cif. Google Scholar

[50] Previously, glutathione was reported to be nonluminescent (see Ref. [8]), our results, however, show it can be emissive under proper conditions. Detailed results will be reported later. Google Scholar

  • Figure 1

    Exampled nonaromatic amino acids and photographs of their recrystallized solids taken under 365 nm UV light. Emission efficiencies of the recrystallized solids are given in brackets (color online).

  • Figure 2

    (a) Emission (λex=365 nm) and (b) absorption spectra of varying L-Lys aqueous solutions; (c) emission spectra of 0.1 M L-Lys aqueous solution with different λexs; (d, e) photographs of varying L-Lys aqueous solutions taken under 365 nm UV light or ceasing the irradiation at room temperature and 77 K (color online).

  • Figure 3

    Emission spectra of recrystallized solids of (a) L-Lys, (b) L-Ser, and (c) L-Ile with td of 0 (solid line) and 0.1 ms (dash line). (d) Microscope images of L-Lys solids taken under illumination of UV (330–385 nm, left), blue (460–495 nm, middle) and green (530–550 nm, right) lights. (e) Photographs of L-Lys, L-Ser, and L-Ile solids taken at 77 K under 365 nm UV light or after ceasing the UV irradiation (color online).

  • Figure 4

    (a, b) Crystal structure of L-Ser with denoted intermolecular interactions around one molecule; (c) N···O and O···O intermolecular interactions around one molecule; (d) fragmental 3D through space electronic communication channel in the L-Ser crystals (color online).

  • Figure 5

    Photographs of (a) different ε-PLL aqueous solutions and (b) solid powders taken under 365 nm UV light or after ceasing the UV irradiation. Emission spectra of (c) different ε-PLL aqueous solutions (λex=336 nm) and (d) 15 mg/mL solution with varying λexs. (e) Normalized emission spectra of ε-PLL solids with td of 0 (solid line) and 0.1 ms (dash line) under varying λexs (color online).

  • Figure 6

    Confocal luminescent images of HeLa cells after incubation with 0.1 M L-Ile in DMEM for 1.5 h. (a) Confocal image recorded under excitation at 405 nm, (b) bright field image, and (c) corresponding overlayed image (color online).

Copyright 2020  CHINA SCIENCE PUBLISHING & MEDIA LTD.  中国科技出版传媒股份有限公司  版权所有

京ICP备14028887号-23       京公网安备11010102003388号