Gelatinous Residue Research Articles

Deep eutectic solvents: green solvents for the removal of degraded gelatin on cellulose nitrate cinematographic films

Cellulose nitrate (CN) has been used in the past as support for photographic negatives and cinematographic films. This material is particularly unstable and can undergoes severe degradation due to thermal, photocatalytic and hydrolytic loss of nitro groups from the lateral chain. Thus, to prevent the disappearance of the movies, their scanning and digitalization become a priority.However, CN bases degradation may prevent the scanning of the films. The decrease in pH, for instance, lowers the viscosity of gelatin, which becomes softer. This causes the formation of gelatin residues which stick on the back of the superimposed frames inside the reels creating a deposit.Traditional approaches to clean gelatin residues from the surface of CN bases include the mechanical removal with scalpels and the use of organic solvents (such as isopropyl alcohol). However, these methods are either slow and ineffective or could potentially damage the degraded CN supports.To overcome these drawbacks, we have evaluated the performance of three choline chloride and betaine-based Deep Eutectic Solvent (DES) formulations as alternative for the removal of gelatine residues from CN supports. These solvents are inexpensive (when compared to traditional solvents), easy to prepare, green (non volatile, safe towards the operators and the environment, and potentially recyclable), non flammable and have been previously proposed for the extraction of proteinaceous materials, but their use for the restoration of photographic negatives or cinematographic films has not been reported yet.Selected areas over the frames of a real deteriorated CN cinematographic film were cleaned comparing the DES performances with the ones obtained using isopropyl alcohol as an example of a traditional method.In particular, the tested DES formulations showed superior cleaning power compared to isopropyl alcohol and, at the selected application times, resulted capable to remove the gelatin residues without affecting the CN film supports.Graphical abstract

Residue Analysis as Evidence of Activity Areas and Phased Abandonment in a Medieval Jordanian Village

During the 2013 and 2014 excavation seasons, a cache of complete ceramic vessels was recovered from a stone-outlined pit sealed by domestic building collapse at the site of Tall ?isb?n, a Mamluk-era rural site in central Jordan. Among the finds were two whole, handless stonepaste jars of the late 14th century—an extremely rare find in Bil?d al-Sh?m—along with a small, handless handmade jar containing a gelatinous residue. Valuable not only for the stratigraphic association of a local coarse ware (of previously unclear chronology) with datable imports, the pit provides the opportunity to explore the realities of site abandonment in a rural setting and the communal experience associated with it. The following study presents the results of recent residue analysis of these jars, as interpreted by the unique conditions of the jars’ deposition and against the backdrop the emerging picture of the household economy of medieval ?isb?n, its food systems, and the fast rise and slow decline of the village in the 14th through the 16th centuries CE. In the process, this essay suggests ways in which rural communities in southern Syria were transformed on the eve of the Ottoman conquest.

Tightening of gelatin chemically crosslinked networks assisted by physical gelation

ABSTRACTDeveloping the use of polymers from renewable sources to build hydrogels with tailored mechanical properties has become an increasing focus of research. The impact of the thermo‐reversible physical networks of gelatin (arising from the formation of triple‐helices) on the structure formation of a chemical network, obtained by crosslinking with glutaraldehyde (a non‐catalytic crosslinker), was studied using optical rotation, oscillatory rheology, and large strain mechanical deformation. We observed a direct correlation between the storage shear modulus of the chemical network grown in the gel state (i.e., simultaneously with the physical network) and the amount of gelatin residues in the triple‐helix conformation (χ). Since χ is directly affected by temperature, the value of the storage modulus is also sensitive to changes in the temperature of gel formation. χ values as low as 12% lead to an increase of the shear storage modulus of the crosslinked gel by a factor of 2.7, when compared to a chemical network obtained in the sol state (i.e., in the absence of a physical network). Our results show that the physical network acts as a template, which leads to a greater density of the chemical crosslinks and a corresponding higher elastic modulus, beyond what is otherwise achieved in the absence of a physical network. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2017, 55, 1850–1858

Production and in vitro evaluation of macroporous, cell-encapsulating alginate fibres for nerve repair

The prospects for successful peripheral nerve repair using fibre guides are considered to be enhanced by the use of a scaffold material, which promotes attachment and proliferation of glial cells and axonal regeneration. Macroporous alginate fibres were produced by extraction of gelatin particle porogens from wet spun fibres produced using a suspension of gelatin particles in 1.5% w/v alginate solution. Gelatin loading of the starting suspension of 40.0, 57.0, and 62.5% w/w resulted in gelatin loading of the dried alginate fibres of 16, 21, and 24% w/w respectively. Between 45 and 60% of the gelatin content of hydrated fibres was released in 1h in distilled water at 37°C, leading to rapid formation of a macroporous structure. Confocal laser scanning microscopy (CLSM) and image processing provided qualitative and quantitative analysis of mean equivalent macropore diameter (48–69μm), pore size distribution, estimates of maximum porosity (14.6%) and pore connectivity. CLSM also revealed that gelatin residues lined the macropore cavities and infiltrated into the body of the alginate scaffolds, thus, providing cell adhesion molecules, which are potentially advantageous for promoting growth of glial cells and axonal extension. Macroporous alginate fibres encapsulating nerve cells [primary rat dorsal root ganglia (DRGs)] were produced by wet spinning alginate solution containing dispersed gelatin particles and DRGs. Marked outgrowth was evident over a distance of 150μm at day 11 in cell culture, indicating that pores and channels created within the alginate hydrogel were providing a favourable environment for neurite development. These findings indicate that macroporous alginate fibres encapsulating nerve cells may provide the basis of a useful strategy for nerve repair.

Biomimetic Synthesis of Gelatin Polypeptide-Assisted Noble-Metal Nanoparticles and Their Interaction Study.

Herein, the generation of gold, silver, and silver–gold (Ag–Au) bimetallic nanoparticles was carried out in collagen (gelatin) solution. It first showed that the major ingredient in gelatin polypeptide, glutamic acid, acted as reducing agent to biomimetically synthesize noble metal nanoparticles at 80°C. The size of nanoparticles can be controlled not only by the mass ratio of gelatin to gold ion but also by pH of gelatin solution. Interaction between noble-metal nanoparticles and polypeptide has been investigated by TEM, UV–visible, fluorescence spectroscopy, and HNMR. This study testified that the degradation of gelatin protein could not alter the morphology of nanoparticles, but it made nanoparticles aggregated clusters array (opposing three-dimensional α-helix folding structure) into isolated nanoparticles stabilized by gelatin residues. This is a promising merit of gelatin to apply in the synthesis of nanoparticles. Therefore, gelatin protein is an excellent template for biomimetic synthesis of noble metal/bimetallic nanoparticle growth to form nanometer-sized device.

Hydrogen Exchange and Hydration Dynamics in Gelatin Gels

Gelatin, derived from the collagen triple helix, is the most widely used functional biopolymer and a prototype for studies of physical gels. Gelatin gels have also served as models for soft biological tissue in efforts to elucidate the molecular basis of the magnetic relaxation phenomena that govern magnetic resonance image contrast. Yet, the microstructure, hydration, and magnetic relaxation behavior of gelatin gels are not well understood. To address these issues, we report here the water 2H and 17O magnetic relaxation dispersion (MRD) profiles from gelatin gels over wide ranges of resonance frequency and pH. For the global analysis of this extensive data set, we use a generalized relaxation theory that remains valid for arbitrarily slow molecular dynamics. The strong pH dependence in the 2H profiles can be rationalized quantitatively as the result of exchange with bulk water of labile hydrogens in gelatin side chains. The global analysis of the MRD data yields hydrogen-exchange rate constants, acid dissociation constants, and orientational order parameters in agreement with independent structural, thermodynamic, and kinetic data. The MRD analysis reveals a highly mobile hydration layer at the surface of the gelatin triple helix and a small number of trapped water molecules with residence times on the order of 10(-8) s, presumably associated with structural defects and branch points in the gel. The MRD data also indicate that approximately 20% of the gelatin residues belong to flexible polypeptide chains, rather than to rigid triple-helical segments. By identifying the molecular species and motions responsible for the 2H and 17O dispersion profiles, this study takes a significant step toward a quantitative understanding of water relaxation in aqueous gels and biological tissue.

Aluminum Elicits Exocellular Phosphatidylethanolamine Production in Pseudomonas fluorescens

Pseudomonas fluorescens ATCC 13525 was found to grow in a minimal mineral medium supplemented with millimolar amounts of aluminum, a known environmental toxicant. During the stationary phase of growth, the trivalent metal was localized in a phosphatidylethanolamine (PE)-containing residue. The concentration of PE in pellets ranged from 1.7 to 13.9 mg ml of culture(sup-1) in media supplemented with 1 to 30 mM aluminum. Although the gelatinous residue was observed during the stationary phase of growth, ultracentrifugation and dialysis experiments revealed that PE was produced from earlier stages of incubation and was associated with aluminum. A sharp diminution in the levels of PE and aluminum in the spent fluid was concomitant with the formation of the insoluble deposit. The aluminum content of the soluble cellular fraction increased during growth and reached an optimum of 1.85 mM of test metal at 45 h in cultures with 15 mM aluminum. Further incubation, however, led to a marked decrease in the cellular aluminum content, and during the stationary phase of growth, only trace amounts of the trivalent metal were detected in this fraction. When 45-h cells were incubated in fresh citrate medium, most of the intracellular aluminum was secreted in the spent fluid and citrate was rapidly consumed. Aluminum efflux was also observed in cultures in which d-glucose was substituted for citrate. However, no efflux of this trivalent metal was evident in media devoid of either citrate or d-glucose. Scanning electron microscopic studies and X-ray energy-dispersive analyses of the dialyzed supernatant aided in the visualization of nodule-like aluminum- and phosphorus-rich bodies associated with thread-like carbon-, oxygen-, and phosphorus-containing structures. Transmission electron microscopic and electron energy loss spectroscopic analyses revealed the presence of aluminum within bacteria after 45 h of incubation. Cells harvested after aluminum insolubilization did not shown aluminum inclusions. This aluminum-tolerant microbe may have potential application in bioremediation processes.

Cellular response to a multiple-metal stress in Pseudomonas fluorescens

Pseudomonas fluorescens multiplied in a minimal mineral medium supplemented with millimolar amounts of aluminum (5 mM), iron (5 mM), zinc (3 mM), calcium (2 mM) and gallium (1 mM). A slight decrease in growth rate and a 22% diminution in cellular yield were observed as compared to the control medium. Citrate, the sole source of carbon to which the test metals were complexed, was completely utilized. Although at stationary phase of growth most of the metals were immobilized in an exocellular lipid-rich residue, ultracentrifugation and dialysis studies revealed that metals were associated with phosphatidylethanolamine (PE) from early stages of growth. As growth progressed the metal content of the soluble cellular extract increased reaching an optimum at 35 h of incubation. However, no detectable amounts of metals in this cellular component were discerned at stationary phase of growth. There appeared to be no marked variation in exocellular protein and carbohydrate production in control and metal-stressed cultures. Transmission electron microscopic studies revealed metal rich bodies associated with the cytoplasm. Scanning electron microscopic analyses of the dialyzate aided in the identification of the metal-rich bodies associated with elongated structures comprised of carbon, oxygen and phosphorus. PE appeared to be an important organic constituent of the gelatinous residue.

Exocellular phosphatidylethanolamine production and multiple-metal tolerance in Pseudomonas fluorescens

Pseudomonas fluorescens appeared to circumvent the challenge imposed by millimolar amounts of metals (5 mM Al 3+, 5 mM Fe 3+, 2 mM Ca 2+, 1 mM Ga 3+ and 3 mM Zn 2+) by the formation of phosphatidylethanolamine. This lipid moiety constituted an important organic component of an insoluble gelatinous residue in which most of the test metals were immobilized at stationary phase of growth. Ultracentrifugation and dialysis experiments showed that the metals were associated with phosphatidylethanolamine from early stages of growth. Transmission electron microscopy revealed metal rich bodies in the cytoplasm prior to their secretion in the spent fluid. These results demonstrate a role of phosphatidylethanolamine in multiple-metal homeostasis.

Exocellular phosphatidylethanolamine production and multiple-metal tolerance in Pseudomonas fluorescens

Pseudomonas fluorescens appeared to circumvent the challenge imposed by millimolar amounts of metals (5 mM Al3+, 5 mM Fe3+, 2 mM Ca2+, 1 mM Ga3+ and 3 mM Zn2+) by the formation of phosphatidylethanolamine. This lipid moiety constituted an important organic component of an insoluble gelatinous residue in which most of the test metals were immobilized at stationary phase of growth. Ultracentrifugation and dialysis experiments showed that the metals were associated with phosphatidylethanolamine from early stages of growth. Transmission electron microscopy revealed metal rich bodies in the cytoplasm prior to their secretion in the spent fluid. These results demonstrate a role of phosphatidylethanolamine in multiple-metal homeostasis.

Microbial adaptation to iron: a possible role of phosphatidylethanolamine in iron mineral deposition

Pseudomonas fluorescens multiplied in a minimal mineral medium supplemented with iron(III) (5 mm) complexed to citrate, the sole source of carbon, with no apparent diminution in cellular mass. Atomic absorption studies of different cellular fractions and supernatant at various growth intervals revealed that the trivalent metal was initially internalized. At approximately 41 h of incubation, the soluble cellular extract contained 9.5% of the iron originally found in the growth medium. However, as bacterial multiplication progressed, most of the metal was deposited as an extracellular insoluble gelatinous residue. Phosphatidylethanolamine appeared to be an important organic constituent of this precipitate. X-ray fluorescence and diffraction studies revealed that iron(III) was deposited as amorphous hydrated oxide. Scanning electron microscopy and energy dispersive X-ray microanalysis of the pellet aided in the identification of irregular shaped bodies rich in iron and oxygen that were associated with carbon-containing elongated structures. Examination of the bacterial cells by a transmission electron microscope equipped with an electron energy loss spectrometer indicated the deposition of iron within the cells.

Aluminum tolerance inPseudomonas fluorescensATCC 13525: Involvement of a gelatinous lipid-rich residue

Pseudomonas fluorescens was found to grow in a mineral medium supplemented with up to 50 mM aluminum, complexed to citrate, the sole source of carbon. At stationary phase while virtually no diminution in cellular yield was observed in the presence of 1.0 mM aluminum, only 31% of bacterial yield was recorded in media with 50 mM aluminum. The decrease in soluble aluminum in the culture fluid was concomitant with the formation of a gelatinous residue. At later stages of growth, the trivalent metal was immobilized in this deposit. This bioprecipitate consisted of lipid moieties but was apparently devoid of proteins and carbohydrates. X-ray fluorescence spectroscopy and colorimetric assays also revealed the presence of aluminum and phosphorus. X-ray diffraction spectroscopy indicated that the biomineral was amorphous. Examination of the gelatinous residue by scanning electron microscopy and energy dispersive X-ray microanalysis aided in the identification of aluminum, oxygen and phosphorus rich irregular bodies that were associated with carbon containing thread-like structures.