a b s t r a c tThe durability against light and aging dynamics of heteroatomic aromatic dyes and pigments containing nitrogen atoms used in writing inks was studied using Raman spectroscopy. The mechanisms of their thermal and photo-decomposition were proposed and the rates of these processes were determined. According to Raman spectroscopy, it was found that depending on the presence of one or another colorant, there are three main types (Type A, Type B and Type C) of blue dye inks used in ballpoint, gel and capillary pens which were studied in this work. Each type is characterized by a certain set of signals in Raman spectra. Time dependencies of Raman signal intensities for each type revealed the dynamics of the processes occurred with colorants included in the studied inks from the moment when they were printed on paper. Thus, the results obtained in this study can be used for the age estimation of the paper documents up to 15 years.
This work is devoted to the extremely popular but poorly developed scientific and forensic problem of the estimation of the actual dates of inscriptions placed on paper and made by ballpoint pens. It is shown that the degradation of writing inks with time may be controlled via Raman spectroscopy and gas chromatography. The time intervals for the implementation of each of these methods were determined using the ratios of the Raman peak intensities as degradation characteristics rather than their absolute values. In turn, this eliminates the effect of the concentration of a dye. The mutual influence of the volatile components and dyes of writing inks was also investigated and the time interval within which such influence is critical was found. According to the obtained results, a new methodological scheme for determining the age of documents, which were created at least 40 months ago, was proposed.
Rhodopsins
are seven α-helical membrane proteins that are
of great importance in chemistry, biology, and modern biotechnology.
Any in silico study on rhodopsin properties and functioning requires
a high-quality three-dimensional structure. Due to particular difficulties
with obtaining membrane protein structures from the experiment, in
silico prediction of the three-dimensional rhodopsin structure based
only on its primary sequence is an especially important task. For
the last few years, significant progress was made in the field of
protein structure prediction, especially for methods based on comparative
modeling. However, the majority of this progress was made for soluble
proteins and further investigations are needed to achieve similar
progress for membrane proteins. In this paper, we evaluate the performance
of modern protein structure prediction methodologies (implemented
in the Medeller, I-TASSER, and Rosetta packages) for their ability
to predict rhodopsin structures. Three widely used methodologies were
considered: two general methodologies that are commonly applied to
soluble proteins and a methodology that uses constraints that are
specific for membrane proteins. The test pool consisted of 36 target-template
pairs with different sequence similarities that was constructed on
the basis of 24 experimental rhodopsin structures taken from the RCSB
database. As a result, we showed that all three considered methodologies
allow obtaining rhodopsin structures with the quality that is close
to the crystallographic one (root mean square deviation (RMSD) of
the predicted structure from the corresponding X-ray structure up
to 1.5 Å) if the target-template sequence identity is higher
than 40%. Moreover, all considered methodologies provided structures
of average quality (RMSD < 4.0 Å) if the target-template sequence
identity is higher than 20%. Such structures can be subsequently used
for further investigation of molecular mechanisms of protein functioning
and for the development of modern protein-based biotechnologies.
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