Development of eye phantom for mimicking the deformation of the human cornea accompanied by intraocular pressure alterations.

Comparative studies between artificial eyeball phantoms and in-vivo human subjects were carried out to better understanding the structural deformation of the cornea under varying intraocular pressure (IOP). The IOP-induced deformation and the tension of the cornea were measured by using an optical coherence tomography and noncontact tonometer readings, respectively. The dependence of the central cornea thickness (CCT) and corneal radius of curvature (CRC) on the IOP differed significantly between the full eyeball phantom (FEP) and cornea eyeball phantom (CEP) models. While the CCT changes were very similar between the two models, the relation between the CRC and the IOP was dependent on the type of eye phantom. For the CEP, the CRC drastically decreased as internal pressure increased. However, we found that the changes in the CRC of FEP was dependent on initial CCT under zero IOP (CCT0). When CCT0 was less than 460 µm, the CRC slightly decreased as IOP increased. Meanwhile, the CRC increased as IOP increased if CCT0 was 570 µm. A constitutive mechanical model was proposed to describe the response of the cornea accompanied by the changes in IOP. In vivo measurements on human subjects under both noninvasive and invasive conditions revealed that the relation between the CRC on the IOP is much closer to those observed from FEP. Considering the observed structural deformation of human cornea, we found that FEP mimics the human eye more accurately than the CEP. In addition, the tonometry readings of IOP show that the values from the CEP were overestimated, while those from the FEP were not. For these reasons, we expect that the FEP could be suitable for the estimation of true IOP and allow performance testing of tonometers for medical checkups and other clinical uses.

Hydrophobic Residues near the Bilin Chromophore-Binding Pocket Modulate Spectral Tuning of Insert-Cys Subfamily Cyanobacteriochromes.

Cyanobacteriochromes (CBCRs) are a subfamily of phytochrome photoreceptors found exclusively in photosynthetic cyanobacteria. Four CBCRs containing a second Cys in the insert region (insert-Cys) have been identified from the nonheterocystous cyanobacterium Microcoleus B353 (Mbr3854g4 and Mbl3738g2) and the nitrogen fixing, heterocystous cyanobacterium Nostoc punctiforme (NpF2164g3 and NpR1597g2). These insert-Cys CBCRs can sense light in the near-UV to orange range, but key residues responsible for tuning their colour sensitivity have not been reported. In the present study, near-UV/Green (UG) photosensors Mbr3854g4 (UG1) and Mbl3738g2 (UG2) were chosen for further spectroscopic analysis of their spectral sensitivity and tuning. Consistent with most dual-Cys CBCRs, both UGs formed a second thioether linkage to the phycocyanobilin (PCB) chromophore via the insert-Cys. This bond is subject to breakage and relinkage during forward and reverse photoconversions. Variations in residues equivalent to Phe that are in close contact with the PCB chromophore D-ring in canonical red/green CBCRs are responsible for tuning the light absorption peaks of both dark and photoproducts. This is the first time these key residues that govern light absorption in insert-Cys family CBCRs have been identified and characterised.

Selective disruption of vascular endothelium of zebrafish embryos by ultrafast laser microsurgical treatment.

In this work, we demonstrate that ultrafast laser irradiation could selectively disrupt vascular endothelium of zebrafish embryos in vivo. Ultrafast lasers minimize the collateral damage in the vicinity of the laser focus and eventually reduce coagulation in the tissues. We have also found that the threshold fluence for lesion formation of the vascular endothelium strongly depends on the developmental stage of the embryos. The threshold laser fluence required to induce apparent lesions in the vascular structure for Somite 14, 20 and 25 stages is about 5 J/cm(2) ~7 J/cm(2), which is much lower than that for the later development stages of Prim 16 and Prim 20 of 30 J/cm(2) ~50 J/cm(2). The proposed method for treating the vascular cord of zebrafish embryos in the early stage of development has potential as a selective and effective method to induce a fatal lesion in the vascular endothelium without damaging the developed blood vessels.

Dynamic changes in PDMS surface morphology in femtosecond laser treatment.

We have investigated the effect of the dynamics of crater size on the poly(dimethylsiloxane) (PDMS) surface morphology in fs-laser micro-processing. PDMS surface was processed with varying both inter-pulse interval and inter-spot distance between successive laser pulses. With keeping the interval of 5 ms crater shape is round even if the spot is overlapped in space. But decreasing the interval to 0.02 ms the shape of the crater is no longer round. Decreasing the inter-distance between the craters results in roughened surface morphology even at time intervals of 5 ms. Temporal dependence of single-shot fs-laser induced crater size was measured as a function of time delay. Within 0.1 ms after pulse irradiation with a fluence of 4.8 J/cm2 on PDMS surface the crater size has reached to its maximum values and then decreased with a time constant of about 0.3 ms. The surface morphology after fs-laser pulse irradiation is strongly dependent on not only inter-spot distance between successive laser pulse but also their inter-pulse intervals. By proposing a theoretical model on their dynamic features, we will try to explain the current observation in quantitatively.

Genomic Survey and Biochemical Analysis of Recombinant Candidate Cyanobacteriochromes Reveals Enrichment for Near UV/Violet Sensors in the Halotolerant and Alkaliphilic Cyanobacterium Microcoleus IPPAS B353.

Cyanobacteriochromes (CBCRs), which are exclusive to and widespread among cyanobacteria, are photoproteins that sense the entire range of near-UV and visible light. CBCRs are related to the red/far-red phytochromes that utilize linear tetrapyrrole (bilin) chromophores. Best characterized from the unicellular cyanobacterium Synechocystis sp. PCC 6803 and the multicellular heterocyst forming filamentous cyanobacteria Nostoc punctiforme ATCC 29133 and Anabaena sp. PCC 7120, CBCRs have been poorly investigated in mat-forming, nonheterocystous cyanobacteria. In this study, we sequenced the genome of one of such species, Microcoleus IPPAS B353 (Microcoleus B353), and identified two phytochromes and seven CBCRs with one or more bilin-binding cGMP-specific phosphodiesterase, adenylyl cyclase and FhlA (GAF) domains. Biochemical and spectroscopic measurements of 23 purified GAF proteins from phycocyanobilin (PCB) producing recombinant Escherichia coli indicated that 13 of these proteins formed near-UV and visible light-absorbing covalent adducts: 10 GAFs contained PCB chromophores, whereas three contained the PCB isomer, phycoviolobilin (PVB). Furthermore, the complement of Microcoleus B353 CBCRs is enriched in near-UV and violet sensors, but lacks red/green and green/red CBCRs that are widely distributed in other cyanobacteria. We hypothesize that enrichment in short wavelength-absorbing CBCRs is critical for acclimation to high-light environments where this organism is found.

Interaction of metallo- and free base meso-tetrakis(N-methylpyridium-4-yl)porphyrin with a G-quadruplex: effect of the central metal ions.

The effects of the central metal ion on complex formation between meso-tetrakis(N-methylpyridium-4-yl)porphyrin (TMPyP) and the thrombin-binding aptamer G-quadruplex, 5'G2T2G2TGTG2T2G2, were examined in this study. The central metal ions were vanadium and zinc. At a [porphyrin]/[G-quadruplex] ratio of less than one, the absorption and CD spectra were unaffected by the mixing ratio for all three porphyrins, suggesting that the binding mode is homogeneous. Relatively small changes in the absorption spectrum when forming the complexes with the G-quadruplex, the positive CD signal, and the large accessibility of the I(-) quencher, suggested that all these porphyrins are not intercalated between the G-quartet. Stabilization of the G-quadruplex by ZnTMPyP was most effective. The effect of VOTMPyP on G-quadruplex stabilization was moderate, whereas TMPyP slightly destabilized G-quadruplex. From this observation, the involvement of the ligation of one G-quartet component to the central metal ion in G-quadruplex stabilization by metallo-TMPyP is suggested.

Femtosecond laser-assisted selective reduction of neovascularization in rat cornea.

Nonlinear multiphoton absorption induced by focusing near infrared (NIR) femtosecond (fs) laser pulses into a transparent cornea allows surgery on neovascular structures with minimal collateral damage. In this report, we introduce an fs laser-based microsurgery for selective treatment of rat corneal neovascularizations (in vivo). Contiguous tissue effects are achieved by scanning a focused laser pulse below the corneal surface with a fluence range of 2.2-8.6 J/cm(2). The minimal visible laser lesion (MVL) threshold determined over the corneal neovascular structures was found to be 4.3 J/cm(2). Histological and optical coherence tomography examinations of the anterior segment after laser irradiations show localized degeneration of neovascular structures without any unexpected change in adjacent tissues. Furthermore, an approximately 30 % reduction in corneal neovascularizations was observed after 5 days of fs laser exposure. The femtosecond laser is thus a promising tool for minimally invasive intrastromal surgery with the aid of a significantly smaller and more deterministic photodisruptive energy threshold for the interaction between the fs laser pulse and corneal neovascular structures.

Micro-structuring of CIGS thin-film coated on Mo back contact by ultrafast laser 'rail-roading' patterning.

We report selective patterning process, laser 'rail-roading' scribing method, of which operating principle is based on transient force balance between the material properties including cohesion and adhesion forces subjected to underlying substrate and laser-induced shock compression and shear forces. By using dual fs-laser beam lines with an interval larger than laser spot size, we provide a proof of the concept by patterning the photovoltaic modules based on CIGS (Cu(In,Ga)Se2) coated on Mo electrode. With varying the interval between the two laser beam tracks, we can provide intact Mo back contact surface without any residues in a manner of more facile, high-speed and high scribing efficiency. We have interpreted the effect of the ambient gases and grooving width on the scribing performance in terms of the cohesion forces between the grains of CIGS thin films as well as adhesion force between underlying Mo layer and CIGS, which are mainly governed by local laser ablation and peening process followed by laser-induced shock compression, respectively.

Ethylene suppression of sugar-induced anthocyanin pigmentation in Arabidopsis.

Anthocyanin accumulation is regulated negatively by ethylene signaling and positively by sugar and light signaling. However, the antagonistic interactions underlying these signalings remain to be elucidated fully. We show that ethylene inhibits anthocyanin accumulation induced by sucrose (Suc) and light by suppressing the expression of transcription factors that positively regulate anthocyanin biosynthesis, including GLABRA3, TRANSPARENT TESTA8, and PRODUCTION OF ANTHOCYANIN PIGMENT1, while stimulating the concomitant expression of the negative R3-MYB regulator MYBL2. Genetic analyses show that the ethylene-mediated suppression of anthocyanin accumulation is dependent upon ethylene signaling components responsible for the triple response. Furthermore, these positive and negative signaling pathways appear to be under photosynthetic control. Suc and light induction of anthocyanin accumulation was almost fully inhibited in wild-type Arabidopsis (Arabidopsis thaliana) ecotype Columbia and ethylene (ethylene response1 [etr1-1]) and light (long hypocotyl1 [hy1], cryptochrome1/2, and hy5) signaling mutants treated with the photosynthetic electron transport inhibitor 3-(3,4-dichlorophenyl)-1,1-dimethylurea. The transcript level of the sugar transporter gene SUC1 was enhanced in ecotype Columbia treated with the ethylene-binding inhibitor silver and in etr1-1, ethylene insensitive2 (ein2-1), and ein3 ein3-like1 mutants. In contrast, 3-(3,4-dichlorophenyl)-1,1-dimethylurea treatment reduced SUC1 expression, which indicates strongly that SUC1 represents an integrator for signals provided by sugar, light, and ethylene. SUC1 mutations lowered accumulations of anthocyanin pigment, soluble sugar content, and ethylene production in response to Suc and light signals. These data demonstrate that the suppression of SUC1 expression by ethylene inhibits Suc-induced anthocyanin accumulation in the presence of light and, hence, fine-tunes anthocyanin homeostasis.

Visualization of Bonghan microcells by electron and atomic force microscopy.

OBJECTIVES: The origin of adult stem cells remains an open question. If they derive from embryos, it is difficult to determine the mechanism which interrupts their differentiation during tissue formation. In the 1960s, the Bonghan microcell was suggested as one possible, yet to be described, route of stem cell production, such that they have the potential to proliferate to produce normal cells. MATERIALS AND METHODS: In this study, Bonghan microcells were isolated from Bonghan tissues on rat organ surfaces, and their detailed morphology examined by electron and atomic force microscopy. RESULTS: The ultrastructure observed distinguished them from apoptotic bodies and other microorganisms, and their unique, possible proliferation feature, as protruding threads, was imaged by atomic force microscopy. CONCLUSIONS: The unique threadlike structure of the Bonghan microcell is consistent with Prof. Kim's observation in the first step of making a cell. Understanding of the functions of this threadlike structure may give a clue to understand the origin or the differentiation cue of adult stem cells.

Formation of superhydrophobic poly(dimethysiloxane) by ultrafast laser-induced surface modification.

The formation of hemispherical nanostructures and microscaled papilla by ultrafast laser irradiation was found to be a potential method to generate superhydrophbic surface of synthetic polymers. Irradiation of femtosecond laser creates roughened poly(dimethylsiloxane) (PDMS) surface in nano- and microscales, of which topography fairly well imitate a Lotus leaf in nature. The modified surface showed superhydrophobicity with a contact angle higher than 170 degrees as well as sliding angle less than 3 degrees. We further demonstrated that negative replica of the processed PDMS surface exhibit large contact angle hysteresis with a sliding angle of 90 degrees while the positive replica maintains superhydrophobicity.

Thickness dependent CARS measurement of polymeric thin films without depth-profiling.

Coherent anti-Stokes Raman scattering (CARS) microscopy is demonstrated to be a promising optical method for the characterization of polymer films with film thickness varying between 180 nm to 4300 nm. In case of PMMA films with a thickness of few hundreds of nanometers, the observed CARS signal was mainly associated with the interference effect of large nonresonant CARS field from glass substrate and the weak resonant field of PMMA. The dependence of resonant CARS intensity of PMMA film on film thickness is in good agreement with the theoretical prediction on a CARS field. The current work offers potential possibilities of noninvasive thickness measurement of polymeric thin film of thickness less than 180 nm by multiplex CARS microscopy without depth-profiling.

Polarization-induced size control and ablation dynamics of Ge nanostructures formed by a femtosecond laser.

We report a method for controlling the size of a Ge (germanium) nanostructure by changing the angle between the ultrafast laser polarization and the crystal axis of Ge. The nanostructure size dependence on the laser polarization with respect to the Ge crystal axis exhibits a sinusoidal function with a minimum size at (100) axis. Moreover, the measurement of transient reflection reveals the presence of large anisotropies in both its amplitude and its relaxation dynamics with a minimum at (100) crystal axis. This implies that the observed anisotropic dependence of nanostructure size of Ge is followed by a different carrier density as well as its relaxation process, depending on the orientation of the Ge crystal axis only at near and above threshold fluence.

Formation of photoluminescent germanium nanostructures by femtosecond laser processing on bulk germanium: role of ambient gases.

We present preparation of Ge nanostructures formed using by femtosecond laser pulse and origin of visible photoluminescence (PL) properties. High intensity of incident laser energy gives rise to make oxidized layer to surface of Ge nanoparticle after irradiation. Moreover, size dependent Raman shift and PL spectrums are observed with different fluences and various process surroundings. It is noted that the oxidation of Ge nanoparticle formed ambient surroundings plays an important role of photoluminescence.

Protic solvent effects on the photophysical properties of O=Ti(IV)TSPP: photoinduced electron transfer.

The photophysical properties of oxotitanium(IV)meso-tetra(4-sulfonatophenyl) porphyrin (O=Ti(IV)TSPP) have been investigated in water and methanol by laser spectroscopic techniques. The fluorescence emission spectrum of O=Ti(IV)TSPP in methanol exhibits two strong emission bands at 610 and 670 nm at room temperature with the decay time of ca. 310 +/- 10 ps and the rise time shorter than 30 ps, in contrast to the extremely weak emission with the decay time of ca. 27 +/- 4 ps in water, indicating that the fluorescence emissive states are different in the two solvents as supported by the solvent dependences of the excitation spectrum. The transient Raman spectra of O=Ti(IV)TSPP in water has been observed to exhibit a remarkable enhancement of phenyl-related mode at 1599 cm(-1), while in methanol, the Raman frequencies of the porphyrin skeletal modes (upsilon2 and upsilon4) are down-shifted without any apparent enhancement of the phenyl-related mode, indicating different interactions of the two solvents with the excited O=Ti(IV)TSPP. These Raman studies reveal that methanol molecule interacts with the photoexcited O=Ti(IV)TSPP more strongly than water, forming the exciplex, O=Ti(IV)TSPP(MeOH)*, suggesting that the two different emissive states are the singlet Franck-Condon state and the exciplex state in methanol and water, respectively. A broad triplet transient absorption of O=Ti(IV)TSPP has been also observed at 480 nm in water as well as in methanol, which is decreased upon addition of methyl viologen (MV2+) with appearance of a new absorption band at 620 nm. This indicates that the photoinduced electron transfer (PET) takes place from the porphyrin to MV2+ in both solvents. The kinetic analysis of the transient absorption band exhibits the PET rate constants of 4.76 x 10(5) s(-1) and 3,03 x 10(4) s(-1) in methanol and water, respectively. All these results infer that the PET takes place from the (d,pi) CT state and the triplet state of the excited porphyrin in methanol and water, respectively.