4 Crystal Nucleation of Proteins Induced by Surface …
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impossible for practical use to construct this nanostructure in a protein crystallization vessel. Localized plasmon resonance has been reported to occur on incompletely
deposited metal films. In this study, we examined the effect of protein crystallization
promotion by inducing plasmon resonance by thinly sputtered gold.
A sputtered gold film was thinly formed on a glass substrate. A gold sputtering
apparatus for electron microscope (JEOL JFC-1500) used for preparation of SEM
observation sample was used for the sputtered film preparation. The sample was
prepared so that the thickness of the sputter was adjusted to 0–60 nm. Figure 4.5
shows the absorption spectrum of the sputtered film. An absorption peak appeared
at 560 nm on the 10 nm thick substrate. This can be interpreted as that local plasmon
resonance occurred because gold was in an island shape at the initial stage of sputtered
deposition and had a structure similar to that of gold nanoparticles. As the thickness
of the sputtered film was increased, the localized plasmon resonance at 560 nm
disappeared, and broad absorption appeared at 500–1000 nm. This absorption is
called gap mode plasmon resonance and is a characteristic spectrum of plasmon
resonance caused by a film defect. Crystallization experiments were carried out with
this substrate.
A protein solution was dropped using a crystallization vessel on which the gold
thin film was sputtered, and visible light was irradiated. The crystallization experiment used a metastable state of supersaturation 3 ribonucleaseA solution. The
experiment was carried out at a film thickness of 20 nm. The results are shown
in Fig. 4.6. Crystals appeared under the condition of gold evaporation and light irradiation. From this result, we confirmed the effect of promoting crystallization when
exciting localized plasmon in a thin and incompletely deposited film.
This method does not care about the problem of denaturation caused by excessive
light and can obtain the effect of promoting crystallization without changing the
experimental method conventionally carried out by researchers in the field of drug
discovery. I think that it is useful.
Fig. 4.5 Absorption
spectrum of gold-sputtered
thin film. The plasmon
resonance of gold particles is
visible at a film thickness of
10 nm, but gap mode
absorption appears at a film
thickness of 20 nm
77
impossible for practical use to construct this nanostructure in a protein crystallization vessel. Localized plasmon resonance has been reported to occur on incompletely
deposited metal films. In this study, we examined the effect of protein crystallization
promotion by inducing plasmon resonance by thinly sputtered gold.
A sputtered gold film was thinly formed on a glass substrate. A gold sputtering
apparatus for electron microscope (JEOL JFC-1500) used for preparation of SEM
observation sample was used for the sputtered film preparation. The sample was
prepared so that the thickness of the sputter was adjusted to 0–60 nm. Figure 4.5
shows the absorption spectrum of the sputtered film. An absorption peak appeared
at 560 nm on the 10 nm thick substrate. This can be interpreted as that local plasmon
resonance occurred because gold was in an island shape at the initial stage of sputtered
deposition and had a structure similar to that of gold nanoparticles. As the thickness
of the sputtered film was increased, the localized plasmon resonance at 560 nm
disappeared, and broad absorption appeared at 500–1000 nm. This absorption is
called gap mode plasmon resonance and is a characteristic spectrum of plasmon
resonance caused by a film defect. Crystallization experiments were carried out with
this substrate.
A protein solution was dropped using a crystallization vessel on which the gold
thin film was sputtered, and visible light was irradiated. The crystallization experiment used a metastable state of supersaturation 3 ribonucleaseA solution. The
experiment was carried out at a film thickness of 20 nm. The results are shown
in Fig. 4.6. Crystals appeared under the condition of gold evaporation and light irradiation. From this result, we confirmed the effect of promoting crystallization when
exciting localized plasmon in a thin and incompletely deposited film.
This method does not care about the problem of denaturation caused by excessive
light and can obtain the effect of promoting crystallization without changing the
experimental method conventionally carried out by researchers in the field of drug
discovery. I think that it is useful.
Fig. 4.5 Absorption
spectrum of gold-sputtered
thin film. The plasmon
resonance of gold particles is
visible at a film thickness of
10 nm, but gap mode
absorption appears at a film
thickness of 20 nm