• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.70-75
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• 2015

Fasciclin 1 (FAS1) is an extracellular protein whose aggregation in cornea leads to visual impairment. While a number of FAS1 mutants have been studied that exhibit enhanced/decreased aggregation propensity, no structural information has been provided so far that is associated with distinct aggregation potential. In this study, we have investigated the structural and thermodynamic characteristics of the wild-type FAS1 and its two mutants, R555Q and R555W, by using molecular dynamics simulations and three-dimensional reference interaction site model (3D-RISM) theory. We find that the hydrophobic solvent accessible surface area increases due to hydrophobic core repacking in the C-terminus caused by the mutation. We also find that the solvation free energy of the mutants increases due to the enhanced non-native H-bonding. These structural and thermodynamic changes upon mutation contribute to understand the aggregation of these mutants.

• BMB Reports
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• v.51 no.6
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• pp.265-273
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• 2018

Tau protein is encoded in the microtubule-associated protein tau (MAPT) gene and contributes to the stability of microtubules in axons. Despite of its basic isoelectric point and high solubility, tau is often found in intraneuronal filamentous inclusions such as paired helical filaments (PHFs), which are the primary constituent of neurofibrillary tangles (NFTs). This pathological feature is the nosological entity termed "tauopathies" which notably include Alzheimer's disease (AD). A proteinaceous signature of all tauopathies is hyperphosphorylation of the accumulated tau, which has been extensively studied as a major pharmacological target for AD therapy. However, in addition to phosphorylation events, tau undergoes a number of diverse posttranslational modifications (PTMs) which appear to be controlled by complex crosstalk. It remains to be elucidated which of the PTMs or their combinations have pro-aggregation or anti-aggregation properties. In this review, we outline the consequences of and communications between several key PTMs of tau, such as acetylation, phosphorylation, and ubiquitination, focusing on their roles in aggregation and degradation. We place emphasis on the structure of tau protofilaments from the human AD brain, which may be good targets to modulate etiological PTMs which cause tau aggregation.

• BMB Reports
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• v.35 no.6
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• pp.590-594
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• 2002

To elucidate the effect of gamma-irradiation on the molecular properties of myoglobin, the secondary and tertiary structures, as well as the molecular weight size of the protein, were examined after irradiation at various irradiation doses. Gamma-irradiation of myoglobin solutions caused the disruption of the ordered structure of the protein molecules, as well as degradation, cross-linking, and aggregation of the polypeptide chains. A SDS-PAGE study indicated that irradiation caused initial fragmentation of the proteins and subsequent aggregation, due to cross-linking of the protein molecules. The effect of irradiation on the protein was more significant at lower protein concentrations. Ascorbic acid protected against the degradation and aggregation of proteins by scavenging oxygen radicals that are produced by irradiation. A circular dichroism study showed that an increase of the irradiation decreased the a-helical content of myoglobin with a concurrent increase of the aperiodic structure content. Fluorescence spectroscopy indicated that irradiation increased the emission intensity that was excited at 280 nm.

• Biomedical Science Letters
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• v.9 no.4
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• pp.203-207
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• 2003

Protein aggregation could be problematic as causes of diseases and hindrance in the production of useful recombinant proteins. Aggregation of mutant tryptophan synthase $\alpha$-subunits was examined by treatment with urea and at high temperature. Large amorphous aggregate seemed to appear by heat treatment, while more various aggregates in size were formed by treatment with urea at low concentration. The result indicates that different aggregate in size could be formed depending on the treatment condition, suggesting different mechanisms underlying aggregation processes.

• Journal of the Korean Graphic Arts Communication Society
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• v.12 no.1
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• pp.159-168
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• 1994

The Aggregation State of thin vapor deposite Film made by Cyanine Dye were changed into Monomeric molecular state(M) and Dimeric Aggregation(D) at the acidic treatment, into reversible H-Aggregation (H) at alkalic gas or heat treatment. Photo-electric properties were higher H than D and M, this stats were effective in enhancing Photoelectric-conversion characteristic. Substitute group of Meso-Position being stronger electronic Donors, Electronic density is higher and Electric conductivity is enhanced, we confirmed Oscillator Strength calculated by PPP-Molecular Orbital Calculation and Absorption Spectra at solvent stats were agreed good.

• Korean Journal of Pharmacognosy
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• v.53 no.2
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• pp.64-69
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• 2022

When blood vessels are damaged, a rapid hemostatic response should occur in order to lower blood loss and keep normal circulation, and platelet activation and aggregation are essential. Nevertheless, abnormal or excessive platelet aggregation can be a reason of cardiovascular diseases including thrombosis, atherosclerosis, and stroke. Therefore, the screening for a substance which can regulate platelet activation and suppress aggregation reaction is very important for treatment and prevention of cardiovascular diseases. Artemether is a methyl ether derivative of artemisinin, which is isolated from the antimalarial plant Artemisia annua, but research on platelet aggregation or its mechanisms is still insufficient. This study identified the effects of artemether on U46619-induced human platelet aggregation and their granule secretion (ATP and serotonin release). In addition, the effects of artemether on the phosphorylation of PI3K/Akt or MAPK, which are related to signal transduction in platelet aggregation, were studied. As the results, artemether significantly lowered PI3K/Akt and MAPK phosphorylation, which inhibited platelet aggregation through granule secretion (ATP and serotonin release) dose-dependently. Therefore, we suggest that artemether is an antiplatelet substance that regulates PI3K/Akt and MAPK pathway and is of value as a therapeutic and preventive agent for platelet-derived cardiovascular diseases.

• Proceedings of the KIEE Conference
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• 2008.05a
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• pp.165-166
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• 2008

We investigate characteristics of J-aggregation as take advantage of LB technic. In order to confirm the applications possible for the molecular electronic device, the morphological properties of merocyanine dye were investigated by AFM. $\pi$-A curves investigated the surface pressure of the LB film from a liquid to a solid state ranged between 90 and 100 mN/m. We observed aggregation and it's characteristics by using visible reflection spectroscopy. We have observed morphology of merocyanine dye on gold surface by STM. focuses on results obtained in mercocyanide dye of J-aggregation. When LB films of merocyanine dye are mixed with arachidic acid, J-aggregate formation is exhibited. J-aggregate formation has been serving as typical systems in revealing the physical and structural aspects of nano-sized molecular aggregates constructed as muiltilayers.

• Fisheries and Aquatic Sciences
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• v.12 no.3
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• pp.194-202
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• 2009

Sulfated fucans are known to have both anti-thrombotic and anti-coagulant activities. In this study, the variation in platelet aggregation and anti-coagulant activities was investigated in vitro with regard to administered dose, molecular weight distribution, sulfate content, and sugar composition in two algal fucoidans from Eisenia bicyclis and Undaria pinnatifida sporophylls (Mekabu). The anti-coagulant activity largely correlated with sulfate content and with molecular weight distribution in a dose-dependent manner. However, both fucoidans demonstrated inhibitory responses to ADP-induced platelet aggregation in dose- and structure-dependent manners that contrasted with the anti-coagulant activity. Neither molecular weight distribution nor sulfate content greatly affected platelet-aggregation inhibition (PA-inhibition) by the fucoidan fractions, whereas anti-coagulant activity was sensitive to these structural factors. Interestingly, an E. bicyclis fucoidan fraction exhibited almost complete PA-inhibition at a treatment dose of 500 mg/mL while retaining weak anti-coagulant activity. In conclusion, these observations suggest that fucoidan may be a useful anti-thrombotic or anti-platelet agent in various arterial thrombotic disorders, including post-vascular intervention with controlled bleeding complications, due to its anti-coagulant modulating activity.

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3681-3685
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• 2012

We developed a simple and effective method for the SERS-based detection of protein-small molecule complexes and label-free proteins using avidin-induced silver aggregation. Upon excitation with light of the appropriate wavelength (633 and 532 nm), the aggregated silver nanoparticles generate a strong electric field that couples with the resonance of the molecules (atto610 and cytochrome c), increasing the characteristic signals of these molecules and resulting in sensitive detection. The detection limit of biotin with the proposed method is as low as 48 ng/mL. The most important aspect of this method is the induction of silver aggregation by a protein (avidin), which makes the silver more biocompatible. This technique is very useful for the detection of protein-small molecule complexes.

• Bulletin of the Korean Chemical Society
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• v.22 no.3
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• pp.271-275
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• 2001

We investigated H-type molecular aggregation in a simply spin-coated amorphous homopolymer film of polymethacrylate containing push-pull azobenzene moieties. It was found that the aggregate formation was strongly influenced by thermal treatment an d that the aggregate created in the polymer film could be easily disrupted by irradiation of a linearly polarized light. In the first writing cycle of aggregated polymer film, photo-induced birefringence showed a steep increase to the highest value followed by a gradual decrease to the certain asymptotic value under longer irradiation of a linearly polarized light. This unique behavior could be attributed to the cooperative motion and the disruption of the aggregated molecules under continuous irradiation of light.