Intrinsic Nature of the Ultrafast Deexcitation Pathway of Mycosporine-like Amino Acid Porphyra-334

Porphyra-334 is a member of natural UV-screening compounds named mycosporine-like amino acids found in several marine organisms. The UV excited porphyra-334 has been identified to deexcite quickly by puckering the intramolecular cyclohexenimine ring; however, the reason for such a ring-puckering occurrence is yet unclear. In this study, we show the ring-puckering to be the relaxation pathway of the UV excited π electron which shifts from the in-ring bond to the out-of-ring bond. The ring-puckering is characterized by the torsion among the in-ring and out-of-ring bonds. Since the π electron shift is possible in two different directions at the Franck–Condon UV excited state, it enables two ring-puckering pathways: the previously reported pathway and another one newly identified at present. We also examine the ring-unpuckering pathways which are an analogy of cis/trans photoisomerization, and we find them to be not suited for the π electron shift character of the UV excited state and thus not related to the deexcitation pathway. The present study provides insight into how porphyra-334 exerts the UV-screening ability based on its cyclohexenimine ring structure

Improvement of Parameters of the AMBER Potential Force Field for Phospholipids for Description of Thermal Phase Transitions

In this study, we improved parameters of the AMBER potential force field for phospholipids in order to describe the thermal phase transition using molecular dynamic (MD) simulations. To estimate the errors of the main phase transition temperature (<i>T</i>_m), first, MD simulations using the GAFFlipid and Gaff parameters were performed for six phospholipid bilayers, 1,2-dipalmitoyl-<i>sn</i>-glycero-3-phosphocholine (DPPC), 1,2-dipalmitoyl-<i>sn</i>-glycero-3-phosphoethanolamine (DPPE), 1,2-dioleoyl-<i>sn</i>-glycero-3-phosphocholine (DOPC), 1,2-distearoyl-<i>sn</i>-glycero-3-phosphocholine (DSPC), 1-palmitoyl,2-oleoyl-<i>sn</i>-glycero-3-phosphocholine (POPC), and 1-palmitoyl,2-oleoyl-<i>sn</i>-glycero-3-phosphoethanolamine (POPE), with increasing temperature. The <i>T</i>_m values were characterized according to the structural parameter, area per lipid, and gauche ratio in alkyl chains. The <i>T</i>_m values of the six lipids showed ∼50 K differences from the experimentally measured values. To reduce these errors, the well-depth values in the Lennard–Jones potential of the alkyl chains were modified to fit the <i>T</i>_m values of the simulation to the experimental values in a single DPPC bilayer. After the fitting procedure, the <i>T</i>_m values of the six lipids improved, and the errors of <i>T</i>_m improved from ∼50 to ∼15 K. We show that the simulation applying the improved parameters provides more accurate results than the original parameters. These modified parameters were also found to be useful for performing MD simulation of transmembrane proteins with membrane models

Understanding Thermal Phases in Atomic Detail by All-Atom Molecular-Dynamics Simulation of a Phospholipid Bilayer

All-atom molecular dynamics (MD) simulations were used to investigate the thermal phase behavior of two hydrated phospholipids, namely, DPPC and DPPE, at the atomic level. The trajectories in the MD simulations clearly identified the structures of DPPC in the crystalline (L_c), gel (L_β), ripple (P_β), and liquid-crystalline (L_α) phases and those of DPPE in the L_c and L_α phases. The physicochemical and structural properties of these phases agree well with the experimental results. Moreover, the structural transformations between phases were observed. In the L_β phase, forces are directed in opposite directions in the upper and lower layers of the bilayer. These forces, which are due to the thermal motion of each monolayer, strongly influence the series of phase transitions from L_β to P_β. The MD simulations in this work can provide an understanding of the dynamics of the lipid bilayer in each thermal phase and suggest the mechanism that generates the P_β phase

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions

Efficient Surface Peeling, a Photoinduced Result of Photochromic Diarylethene Crystal by Multistep Light Irradiation

Photomechanical materials driven by an external light stimulus have become the focus of much attention. We can operate them in a noncontact way and remotely. Photoinduced bending, one of the typical photomechanical behaviors, is often observed in elongated and thinner crystals, which makes them a promising candidate for a variety of applications. However, the preparation of crystals appropriate for bending behavior is difficult because of the complexity of their molecular structures, preparation conditions, and other factors. Here, an efficient surface peeling of crystals by multistep light irradiation using diarylethene crystals is reported. Thin crystals fabricated by this approach make up less than half the thickness of the original crystals. This shows the potential for the photocontrol of various photomechanical behaviors by the same crystal depending on the irradiation conditions