Lithium Thiocyanate Research Articles

Silk cocoon of Bombyx mori: Proteins and posttranslational modifications – heavy phosphorylation and evidence for lysine‐mediated cross links

Although silk is used to produce textiles and serves as a valuable biomaterial in medicine, information on silk proteins of the cocoon is limited. Scanning electron microscopy was applied to morphologically characterise the sample and the solubility of cocoon in lithium thiocyanate and 2-DE was carried out with multi-enzyme in-gel digestion followed by MS identification of silk-peptides. High-sequence coverage of the silk cocoon proteins fibroin light and heavy chain, sericins and fibrohexamerins was revealed and PTMs as heavy phosphorylation of silk fibroin heavy chain; lysine hydroxylation and Lys->allysine formation have been observed providing evidence for lysine-mediated cross linking of silk as found in collagens, which has not been reported so far. Tyrosine oxidation verified the presence of di-tyrosine cross links. A high degree of sequence conflicts probably representing single-nucleotide polymorphisms was observed. PTM and sequence conflicts may be modulating structure and physicochemical properties of silk.

Preparation of regenerated Antheraea yamamai silk fibroin film and controlled‐molecular conformation changes by aqueous ethanol treatment

AbstractThe methods of dissolving Antheraea yamamai (A. yamamai) silk fibroin fibers and preparing the regenerated silk fibroin were studied. The molecular conformations of A. yamamai silk fibroin film treated by different concentration ethanol solution were investigated by XRD, FTIR, and Raman spectra. The results indicated that A. yamamai silk fibroin fibers could be completely dissolved in dense lithium thiocyanate solution at about 35°C for 1 h. The initial regenerated film consisted of α‐helix and random coil components. The aqueous ethanol treatment of the film resulted in significant increase in β‐sheet component and improvement of water resistance of the film. This effect was strongly dependent on ethanol concentration, and 60–80% (w/w) ethanol was most effective. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Structure and properties of regenerated Antheraea pernyi silk fibroin filaments

AbstractDegummed Antheraea pernyi silk fibroin (APSF) fibers were dissolved in a lithium thiocyanate solution that was dialyzed against distilled water for 3 days. Solution‐cast APSF films were dissolved in hexafluoroisopropanol to prepare a spinning solution. Wet spinning was employed to prepare APSF filaments. Scanning electron microscopy, X‐ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, solid‐state 13C cross‐polarization/magic angle spinning nuclear magnetic resonance, and differential scanning calorimetry were employed to study the regenerated APSF filaments. The results showed a uniform distribution of molecular weights, and the largest one may have been greater than 200 kDa. The regenerated filaments contained β‐sheet, α‐helix, and random‐coil conformations, and their breaking strength was 52.20% of the breaking strength of the native fibers. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

Cathodic electrodeposition of CuSCN thin films

Cathodic electrodepositon of CuSCN thin films on F-doped SnO2 (FTO) substrates has been investigated in aqueous mixed solution of copper perchlorate and lithium thiocyanate. Cathodic current arose around +0.5 V vs. Ag/ AgCl and reached a plateau below ca. +0.3 V in the mixed solution. Levich analysis of the plateau current confirmed limitation of CuSCN deposition by mass transport. The current was proportional almost symmetrically to the concentrations of Cu2+ and SCN-, suggesting that transport of their complex was responsible. Absorption spectrum of the mixed solutions indeed revealed an appearance of a new peak only when both Cu2+ and SCN- were present. Job plot for this peak elucidated formation of 1 to l complex. As the concentration of this active species could be determined from the absorption spectra, Levich analyses at different temperatures made it possible to determine the frequency factor (Do) of and the activation energy (Ea) for the diffusion of (Cu2+)(SCN-) complex as 3.24 x 10-2 cm2 s-1 and 20.1 kJ mol-1 , respectively.

Porous 3‐D scaffolds from regenerated Antheraea pernyi silk fibroin

AbstractIn this study, porous three‐dimensional (3‐D) materials were prepared with the regenerated Antheraea pernyi (A. pernyi) silk fibroin by freeze‐drying from a lithium thiocyanate solution of its fibers. The relationship between preparation conditions and morphological structures of 3‐D materials was also studied. We concluded that with the decrease in A. pernyi silk fibroin solution concentration and the increase in the freezing temperature, the porosity and the average pore diameter of the 3‐D materials were increased while the pore density was decreased. By adjusting the freezing temperature and the silk fibroin solution concentration, the 3‐D materials having the average pore diameter of 75–260 µm and the porosity of 70–90% can efficiently be produced. As a kind of new material with excellent biocompatibility and bioactivity, the material is expected to be applied to tissue regeneration scaffolds. Copyright © 2007 John Wiley & Sons, Ltd.

Structure and properties of regenerated Antheraea pernyi silk fibroin in aqueous solution

Antheraea pernyi silk fibroin fibers were dissolved by aqueous lithium thiocyanate to obtain regenerated A. pernyi silk fibroin solution. By means of circular dichroism, 13C NMR and Raman spectroscopy, the molecular conformation of regenerated A. pernyi silk fibroin in aqueous solution was investigated. The relationship of environmental factors and sol–gel transformation behavior of regenerated A. pernyi silk fibroin was also studied. The molecular conformations of regenerated A. pernyi silk fibroin mainly were α-helix and random coil in solution. There also existed a little β-sheet conformation. It was obviously different with Bombyx mori silk fibroin, whose molecular conformation in solution was only random coil but no α-helix existence. With the increase of temperature and solution concentration and with the decrease of solution pH value, the gelation velocity of regenerated A. pernyi silk fibroin solution increased. Especially, it showed that A. pernyi silk fibroin was more sensitive to temperature than B. mori silk fibroin during the sol–gel transformation. The velocity increased obviously when the temperature was above 30 °C. During the sol–gel transformation, the molecular conformation of regenerated A. pernyi silk fibroin changed from random coil to β-sheet structure. The results of these studies provided important insight into the preparation of new biomaterials by silk fibroin protein.

Controlling molecular conformation of regenerated wild silk fibroin by aqueous ethanol treatment

AbstractRegenerated Antheraea pernyi silk fibroin film was prepared by dissolution of native silk fiber in aqueous lithium thiocyanate. The influence of aqueous ethanol treatment of the dried regenerated film on molecular conformation was studied by X‐ray diffraction, infrared spectroscopy, differential scanning calorimetry, and thermogravimetric analysis. While the initial regenerated film consisted of α‐helix and random coil components, aqueous ethanol treatment of the film resulted in significant increase in β‐sheet component and improvement of water resistance of the film. This effect was strongly dependent on ethanol concentration, and 40–60% (w/w) ethanol was most effective due to balance of hydrophilic/hydrophobic action of the solvent. Copyright © 2003 John Wiley & Sons, Ltd.

Compliant film of regenerated Antheraea pernyi silk fibroin by chemical crosslinking

A compliant film was prepared by chemical crosslinking of fibroin from silk fiber of wild silkworm, Antheraea pernyi. The silk fiber was dissolved in concentrated aqueous lithium thiocyanate and desalinated by dialysis. The film was cast from the regenerated aqueous solution, and crosslinked by polyethylene glycol diglycidyl ether (PEG-DE). This film showed high water resistively while maintaining random coil and α-helix structure, unlike films prepared by organic solvent treatment that causes β-sheet formation. The films containing about 20 wt.% crosslinker were remarkably compliant and tenacious. These features, combined with the living-cell affinity of the wild silkworm fibroin, are expected to be useful in biomedical applications.

Isolation of three main sericin components from the cocoon of the silkworm, Bombyx mori.

To characterize the sericin components of the cocoon of silkworm Bombyx mori, fresh cocoon shells were dissolved in saturated aqueous lithium thiocyanate containing 2-mercaptoethanol, and fractionated by ethanol precipitation. Cocoon sericin was found to mainly consist of three polypeptides having molecular masses of the 400, 250, and 150 kDa estimated by SDS-PAGE, which corresponds to the sericin present in the middle, anterior, and posterior part of the middle silk gland. The amino acid compositions of the 400 and 150 kDa components were similar to each other, but that of the 250 kDa component was different. This suggests differences in the coding gene and properties of the 250 kDa sericin from the other two.

Preparation of undegraded native molecular fibroin solution from silkworm cocoons

The molecular mass of solubilized fibroin prepared from silk was analyzed by SDS-PAGE. It was found that the fibroin molecule was degraded during reeling, degumming (removal of sericin), and dissolution of silk threads. A protocol for the preparation of solubilized fibroin conserving its native molecular size is offered, that is, (1) to use only fresh cocoons (not dry cocoons or reeled silk threads), (2) to degum by heating in 8 M aqueous urea, and (3) to dissolve by saturated (∼9 M) aqueous lithium thiocyanate at room temperature.

Benzo-cis-cyclohexano-14-crown-4 and its lithium thiocyanate complex

The structures of a 14-crown-4 ether containing both benzo and cyclohexano substituents, 2,6,13,17-tetraoxatricyclo-[16.4.0.0(7, 12)]docosa-1(18),19,21-triene, C(18)H(26)O(4), and its lithium complex, [2,6,13,17-tetraoxatricyclo[16.4.0.0(7,12)]docosa-1(18),19, 21-triene-kappa(4)O](thiocyanato-N)lithium(I), [Li(NCS)-(C(18)H(26)O(4))], are presented. The conformation of the free crown, (I), is not preorganized for cation binding, as its donor dipoles are oriented towards opposite sides of the crown ring. The Li(+)-crown complex, (II), exhibits two formula units in the asymmetric unit. The binding conformation observed in (II) does not completely reorient the dipoles to one point, resulting in a long Li-O bond length [2.068 (5) and 2.073 (5) A].

FTIR Spectroscopy of Ion Solvation of LiClO4 and LiSCN in Acetonitrile, Benzonitrile, and Propylene Carbonate

FTIR spectra of lithium perchlorate and lithium thiocyanate in acetonitrile,benzonitrile, and propylene carbonate were recorded in the temperature range from 5to 45°C. New bands due to solvent molecules in the primary solvation shell ofthe lithium ions were detected in the region of the CN stretching mode of thenitriles and of the CO stretching mode of propylene carbonate. The band structureswere studied in detail by deconvolution with band-fitting procedures and meancation solvation numbers were deduced from the band area of the bulk solvent.For the systems acetonitrile—lithium perchlorate, benzonitrile—lithiumperchlorate, and benzonitrile—lithium thiocyanate, solvation numbers of “free” and“bound” lithium ions were calculated with the help of the degree of associationobtained from suitable anion vibrations.

Chemical modification oftussah silk with acid anhydrides

Tussah silk fibroin was chemically modified by acylation with aliphatic, aromatic, and hydrophobic acid anhydrides. The tussah silk fibers were pretreated by immersing them in a lithium thiocyanate (LiSCN) solution and then acylated in dimethylformamide (DMF) at elevated temperatures. Using this method, acylated tussah silk fibers with weight gains of 8–22% could be obtained. The pretreatment with LiSCN was necessary to promote the acylation. Without it, the reaction did not proceed. The optimum temperature and reaction time of the pretreatment was 55°C and 60 min, respectively. When examining the physical properties and the thermal behavior of both pretreated and acylated tussah silk, it was found that the mechanical properties and the position of the major DSC endothermic peak remained unchanged, regardless of pretreatment and acylation. The moisture regain of the pretreated tussah silk increased slightly while the moisture regain of the acylated silk decreased linearly with increasing weight gain. The chemical modification allows for a wide control of the tussah silk fiber's properties, making it possible to use tussah silk for the development and production of novel textile and biomaterials. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 382–391, 2000

New Formulas for Organozincate Chemistry

As a new type of zincate, we designed various new organozinc derivatives, Me3Zn(R)Li2 (R = Me, CN, SCN), which could be prepared in situ from lithium trimethylzincate and anion species such as methyllithium, lithium cyanide, and lithium thiocyanate. We investigated the reactivities of these zincates toward the halogen (or tellurium)−zinc exchange, Michael addition, carbozincation, and epoxide ring opening reactions. On the basis of their excellent chemical yields and chemoselectivities, these species were considered to be differentiated from ordinary triorganozincates, R3ZnLi. We also discuss the structure of the newly designed zincates using 1H NMR/Raman/in situ FTIR/extended X-ray absorption fine structure (EXAFS) spectroscopic and the density-functional theory (DFT) theoretical studies. All results strongly support the fact that these newly designed zincates are a new category of zincate species. This observation is also identical with the fact that newly designed zincates have a higher and unique reac...

Synthesis of cis-p-dioxano-12-crown-4 and X-ray crystallography of the (1:1) complex with lithium thiocyanate

The synthesis of a novel 12-crown-4 analogue (cis-p-dioxano-12-crown-4 or cis-3,6,9,13,15- pentaoxabicyclo[9.3.1]pentadecane) is described. The (1:1) LiNCS complex crystallizes in the monoclinic Cc space group; a = 8.4973(2) Å, b = 18.0659(4) Å, c = 8.9168(1) Å, and β = 90.713(1)° with Z = 4. The crown adopts C1 symmetry to which the Li+ is coordinated in a rectangular pyramid with an apical -NCS.Key words: crown ethers, structure, complexation.

Synthesis of <i>cis</i>-<i>p</i>-dio×ano-12-crown-4 and X-ray crystallography of the (1:1) comple× with lithium thiocyanate

Synthesis of <i>cis</i>-<i>p</i>-dio×ano-12-crown-4 and X-ray crystallography of the (1:1) comple× with lithium thiocyanate

Synthesis and properties of a new series of trögerophanes

AbstractA new series of macrocyclic compounds with one or two Tröger base skeletons has been synthesized by condensing mono‐, di‐, tri‐, and teraethyleneglycol bis(p‐aminophenoxy) ethers with formalin in the presence of concentrated hydrochloric acid in ethanol at room temperature for 13 days. This simple one‐step cyclization provided 19 in remarkably high yield (46%) and 17, 18, and 20 in yields reflecting the strain of the rings and statistical factors. Complexation with lithium thiocyanate was observed for 20, the structure of which was elucidated by X‐ray crystallography.

The effect of thiocyanates on the hydration of portland cement at low temperatures

Sodium thiocyanate, potassium thiocyanate, ammonium thiocyanate, calcium thiocyanate, and lithium thiocyanate were added to Normal Type 10 portland cement in amounts of 1.5 and 3% (with respect to cement on weight basis) and cured at temperatures of 20, 0 and −5°C. The rate of development of heat of hydration, calcium hydroxide content and strength development were followed from a few hours up to 28 days. All thiocyanates increase the early rate of reaction of cement at 20°C. The most efficient early acceleration occurs with 3% Ca(SCN) 2. The total heat of hydration in samples containing KSCN is about 30% more than that registered for the reference at 3 days. At 0°C, there was acceleration in the presence of thiocyanates and the heat of hydration was higher in all the samples containing thiocyanates. All thiocyanates accelerate hydration at −5°C with respect to the reference paste. The reference sample showed practically no hydration even up to 4 days as the water in the pores remained frozen. Some freezing occurred in the presence of NH 4SCN, LiSN and 1.5% Ca(SCN) 2. Calcium thiocyanate accelerates the hydration and strength development in the paste at all curing temperatures. It is the most effective thiocyanate for increasing strengths at low temperatures. After 28 days of curing at −5°C, the cement paste with 3% calcium thiocyanate attains a strength that is 74% of the strength of cement paste cured at 20°C. Sodium thiocyanate is also an effective accelerator and increases strength at low temperatures. The least effective thiocyanates with respect to the development of strengths at −5°C are LiSCN, KSCN and NaSCN at a dosage of 1.5%. A linear relationship exists between the amount of lime formed and strength, within the range of curing periods studied. However, when strength is compared at the same degree of hydration (in terms of lime formed), some pastes exhibit better strengths than others. The relative strengths, therefore, seem to be dependent more on the microstructure of the pastes than on the degree of hydration. At the same degree of hydration at −5°C, 1.5–3% Ca thiocyanate, or 3% Na, K and Li thiocyanates exhibit better strengths than those containing 1.5% Na, Li and K thiocyanates.

A molecular orbital study of bonding and frequency shifts in free and solvated lithium thiocyanate aggregates

The MNDO method has been used to determine the stable structures of lithium thiocyanate aggregates. Two classes of aggregates have been found: (a) N-bonded (LiNCS) p (1 $ ̌ / p⩽ 4) (i.e. linear LiNCS), the rhombic dimer, the triangular trimer and a cubane-like tetramer; (b) (LiSCN) p aggregates (1 $ ̌ / p⩽ 3) with lithium bridges between S and C. The structures of class (a) are in agreement with those experimentally determined in solution; in this case unusual negative frequency shifts of ν(CN) due to μ 2 or gm 3 nitrogen coordination have been reproduced by our vibrational frequency calculations. IR intensity variations are also in qualitative agreement with experiment. The lithium solvation has been simulated by adding water molecules in the first solvation shell of Li in order to complete its coordination number to 4. This model gives a good account of aggregation energies in solution and of ν(CN) frequency variations.

Mixed aggregates between acetylenic lithium compounds and lithium thiocyanate in non-aqueous solutions

The following mixed aggregates between hexynyllithium BuCCLi and lithium thiocyanate, LiNCS, have been characterized by infrared spectroscopy in the ν (CN) region: the mixed species Li 2(BuCC)(NCS) in tetrahydrofuran and dioxane and all three mixed tetranuclear species L 4(BuCC) 3(NCS), Li 4,(BuCC) 2(NCS) 2, Li 4(BuCC)(NCS) 3 in triethylamine. In the same conditions similar species are formed between PhCLi and LiNCS.