Fluorescence of lysine and its derivatives (A) The chemical scheme of lysine and its derivatives comprising shorter carbon chains. (B and C) Microscopy images showing (B) brightfield and (C) fluorescence (excitation at 405 nm) analyses of the four powders. Pixel color represents the intensity; black, non; blue, dim; white, strong. (D) Crystalline structures of lysine and its derivatives as determined using PXRD. See also Data S1 for additional crystallographic information.

Fluorescence of lysine and its derivatives (A) The chemical scheme of lysine and its derivatives comprising shorter carbon chains. (B and C) Microscopy images showing (B) brightfield and (C) fluorescence (excitation at 405 nm) analyses of the four powders. Pixel color represents the intensity; black, non; blue, dim; white, strong. (D) Crystalline structures of lysine and its derivatives as determined using PXRD. See also Data S1 for additional crystallographic information.

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Biomolecule luminescence in the visible range of the spectrum has been experimentally observed upon aggregation, contrary to their monomeric state. However, the physical basis for this phenomenon is still elusive. Here, we systematically examine all coded amino acids to provide non-biased empirical insights. Several amino acids, including non-aroma...

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Context 1
... first inquired whether the length of the amine residue chain of lysine, which has four carbons, plays a role in the optical properties of the crystal. For this purpose, we explored the fluorescence of three additional molecules derived from lysine: L-ornithine, L-2,4-diaminobutyric acid, and DL-2,3-diaminopropionic acid, which comprise 3, 2, and 1 side chain carbons, respectively ( Figure 2A). The rationale of this experiment was to alter the crystal packing by shortening the amine residue, thereby modulating the electronic interactions by varying the distance between molecules, and to examine any effect on the resulting optical properties. ...
Context 2
... four samples (including lysine) comprised small crystalline powders ( Figure 2B). The fluorescent signal from each sample was obtained using confocal microscopy, similar to the amino acids shown in Figure 1. ...
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... fluorescent signals were prominent in the molecules comprising 1-, 2-, and 4-carbon chains, whereas in the 3-carbon chain molecule, ornithine, no visible signal was detected ( Figure 2C). The powder X-ray diffraction (PXRD) patterns of the samples were further examined in order to understand the molecular arrangement of the crystals, which might provide insight into the favorable interactions allowing the crystal fluorescence ( Figure 2D). ...
Context 4
... fluorescent signals were prominent in the molecules comprising 1-, 2-, and 4-carbon chains, whereas in the 3-carbon chain molecule, ornithine, no visible signal was detected ( Figure 2C). The powder X-ray diffraction (PXRD) patterns of the samples were further examined in order to understand the molecular arrangement of the crystals, which might provide insight into the favorable interactions allowing the crystal fluorescence ( Figure 2D). The crystal structures of lysine, ornithine, and diaminopropionic acid were previously published (Chiba et al., 1967;Mar ceková et al., 2019;Williams et al., 2016). ...
Context 5
... the case of cysteine demonstrated in this work, the difference in the molecular packing within the crystal alters the distances between the sulfur atom and the N termini of the neighboring molecule, which could affect the charge transfer potential. Indeed, these distances are shorter for the orthorhombic crystal in comparison with the monoclinic packing ( Figure S2). Overall, on the basis of previous research, it can be summarized that the chromophore responsible for the aggregation-induced absorption and fluorescence in the visible range is structure specific and can be formed either in the absence or presence of aromatic moieties in peptides. ...

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... Interestingly, cysteine displays a crystal structure dependent fluorescence, as different arrangements between two crystal structures result in a reversible on−off optical transition. 34 Thus, the supramolecular assembly of the amino acids clearly has a significant impact on their optical properties. ...
... 19 It is clear, however, that the nature of the electronic transitions underlying the role of the carbonyl groups will be highly sensitive to specific environmental interactions. For example, it would be interesting to investigate in the future the effects of the supramolecular assemblies in lysine or cysteine crystals 34 in the electronic states associated with the carbonyl. ...
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... Concentrationinduced Lys aggregation can also be observed in histones by nonlinear absorbance at 325 nm, and it is hypothesized to involve the α-amino group in Lys-Lys pair coupling [10]. Furthermore, experiments on crystallized Lys and its derivates have demonstrated the important role of supramolecular arrangement in optical emission [11]. ...
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