• Bulletin of the Korean Chemical Society
• /
• v.20 no.3
• /
• pp.333-336
• /
• 1999

The polyaniline films with various insoluble parts are fabricated. The oxidation state (1-y) of these polyaniline is 0.53 and 0.54, respectively. To control the interchain and intrachain interaction of the polymer, the polyaniline films are stretched with appropriate ratio. The insoluble part of polyaniline synthesized at room temperature (low molecular weight) is 12%-76% and that of polyaniline synthesized at 0 'IC (intermediate molecular weight) is 65%-89%. The low molecular weight polyaniline films with various drawing ratios have amorphous structure. In the intermediate weight polyaniline films, the crystallinity of films increases with drawing ratio as well as insoluble part. The difference of the insoluble part affects electrical conductivity which is increased dramatically with draw ratio. In particular, the higher insoluble part caused greater increase in electrical conductivity.

• Applied Chemistry for Engineering
• /
• v.17 no.5
• /
• pp.504-508
• /
• 2006

Molecular weight of polyaniline is controlled in the range of oligomer to low molecular weight by controlling the ratio of aniline dimer (p-aminodiphenylamine) to monomer. Aniline dimers act as nucleation sites in chain growth during the polymerization of aniline. The molecular weights of polyanilines are estimated by GPS and relative viscosity measurement. The physical and chemical properties of polyanilines with various molecular weights are studied by UV-Vis, FT-IR, and electrical conductivity measurements.

• Archives of Reconstructive Microsurgery
• /
• v.2 no.1
• /
• pp.77-81
• /
• 1993

Free tissue transplantation is commonly performed with the brilliant achievement in microsurgery and anticoagulants and antithrombotic agents have been prescribed in the procedures. However, there is no clean-cut indication as to which agents would be more effective in every steps and final consequences. Low molecular weight heparins inhibiting coagulation in plateletrich plasma and acting on the vascular endothelium have antithrombotic and fibrinolysis action. The experiment with rat groin free flap transplantation after 6-hour ischemia and injection of the low molecular weight heparin was performed and the results between the injection and non-injection group were analysed as follows, 1. Both of the 24-hour groups, vessel patency was not proportional to color change of the groin flap. 2. On the second day after anastomois, heparin-injection group showed intact intima, patent lumen without thrombus, and mild granulomatous inflammation around the suture material and control group with doubtful patency revealed intimal loss and thrombus formation. 3. On the 5th, 7th, and 9th postoperative day, heparin group was patent in anastomosis and showed acute inflammatory cells. 4. The 7th-week period, heparin-injection group showed intact flap color, patent lumen with intact intima and persistent foreign body granuloma.

• Biomolecules & Therapeutics
• /
• v.17 no.3
• /
• pp.325-331
• /
• 2009

The object of this study was to evaluate the single oral dose toxicity of Low Molecular Weight Fucoidan (LMF) in male and female rats. LMF was administered to female and male SD rats as an oral dose of 2,000, 1,000 and 500 mg/kg (body wt.). Animals were monitored for the mortality and changes in body weight, clinical signs and gross observation organ weight and histopathology of 14 principle organs were examined upon necropsy. As the results, no LMF treatment related mortalities, clinical signs, changes on the body and organ weights, gross and histopathological observations against 14 principle organs were detected up to 2,000 mg/kg in both female and male rats except for some sporadic findings not LMF treatment related toxicological signs. Therefore, $LD_{50}$ (50% lethal dose) and approximate LD of LMF after single oral treatment in female and male rats were considered over 2,000 mg/kg - the limited dosages recommended by KFDA Guidelines [2005-60, 2005], respectively.

• Proceedings of the Botanical Society of Korea Conference
• /
• 2000.04a
• /
• pp.22-22
• /
• 2000

• Mass Spectrometry Letters
• /
• v.12 no.3
• /
• pp.81-84
• /
• 2021

Collagen, which accounts for one-third of human protein, is reduced due to human aging, and much attention is focused on making collagen into food to prevent such aging. Gel permeation chromatography with Reflective Index (RI) detection (GPC/RI) was chosen as the most suitable instrument to confirm molecular weight distribution, and we explored the use of this technique for analysis of collagen peptide molecular sizes and distributions. Data reliability was verified by matrix-assisted laser desorption/ionization coupled to time-of-flight (MALDI-TOF) mass spectrometric analysis. The data were considered meaningful for comparative analysis of molecular weight distribution patterns.

• Korean Journal of Food Science and Technology
• /
• v.25 no.3
• /
• pp.264-269
• /
• 1993

Molecular structural properties of legume starches were investigated. In intrinsic viscosity and degree of Polymerization of amylose and amylopectins, cow pea and mung bean were high, but kidney bean was low. Low molecular weight fractions for kidney bean starch were much eluted by gel chromatography. In the elution profiles of their amylose by Sepharose 2B-CL, molecular weight of kidney bean amylose was smaller than that of other amylose Molecular weights of cow pea and mung bean amyloses were large, but that of kidney bean amylose was small and red bean amylose was medium. The elution profiles by Sephadex G-50 after debranching amylopectins with pullulanase showed similar patterns.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.8
• /
• pp.1554-1560
• /
• 2008

The probe diffusion and friction constants of methyl yellow (MY) in liquid n-alkanes of increasing chain length were calculated by equilibrium molecular dynamics (MD) simulations at temperatures of 318, 418, 518 and 618 K. Lennard-Jones particles with masses of 225 and 114 g/mol are modeled for MY. We observed that the diffusion constant of the probe molecule follows a power law dependence on the molecular weight of nalkanes, DMY${\sim}M^{-\gamma}$ well. As the molecular weight of n-alkanes increases, the exponent $\gamma$ shows sharp transitions near n-dotriacontane ($C_{32}$) for the large probe molecule (MY2) at low temperatures of 318 and 418 K. For the small probe molecule (MY1) $D_{MY1}$ in $C_{12}$ to C80 at all the temperatures are always larger than Dself of n-alkanes and longer chain n-alkanes offer a reduced friction relative to the shorter chain n-alkanes, but this reduction in the microscopic friction for MY1 is not large enough to cause a transition in the power law exponent in the log-log plot of DMY1 vs M of n-alkane. For the large probe molecule (MY2) at high temperatures, the situation is very similar to that for MY1. At low temperatures and at low molecular weights of n-alkanes, $D_{MY2}$ are smaller than $D_{self}$ of n-alkanes due to the relatively large molecular size of MY2, and MY2 experiences the full shear viscosity of the medium. As the molecular weight of n-alkane increases, $D_{self}$ of n-alkanes decreases much faster than $D_{MY2}$ and at the higher molecular weights of n-alkane, MY2 diffuses faster than the solvent fluctuations. Therefore there is a large reduction of friction in longer chains compared to the shorter chains, which enhances the diffusion of MY2. The calculated friction constants of MY1 and MY2 in liquid n-alkanes supported these observations. We deem that this is the origin of the so-called“solventoligomer”transition.

• Journal of Ginseng Research
• /
• v.19 no.3
• /
• pp.244-248
• /
• 1995

Water-soluble browning pigments were artily purified from Korean red ginseng through the several procedures such as fractionation by n-butanol, precipitation by ethanol, dialysis and gel filtration. At least four kinds of water-soluble browning pigment were separated from each other, two kinds of low-molecular-weight and two kinds of high-molecular-weight pigments.

• KSBB Journal
• /
• v.13 no.1
• /
• pp.96-100
• /
• 1998

Two promoters (trc and P$\rho$) were inserted in PHA operon derived from Alcaligenes eutrophus to obtain high chain molecules of polyhydroxybutyrate (PHB) in recombinant Escherichia coli. Newly designed PHA operon was used to control the gene expressions of hydroxybutyric CoA and PHA polymerization, separately. Plasmids containing new synthetic operon was transformed into E. coli DH5$\alpha$ and analyzed for PHB production. Without induction of the PHA biosynthetic operon, PHA synthase which has low activity might supply low concentration of initiator during the polymerization reaction, resulting very high molecular weight of polymer. An increase of PHB average molecular weight was observed with decreased IPTG (isopropyl $\beta$ -Dithiogalactosidase) concentration. When no IPTG was added to the culture of E. coli DH5$\alpha$ /$\rho$ SJS1 which contained two promoters in PHA operon, high chain polymer having an average molecular weight of $2.5{\times}10^7$ was achieved. Analysis of the enzyme activities of PHA biosynthetic enzymes suggests that PHA synthase, the enzyme responsible for polymerizing 3-hydroxybutyric CoA, controls the molecular weight of PHB produced in vivo.