Cytogenetic studies were conducted with Podocnemis expansa and Podocnemis sextuberculata, turtles of the Brazilian Amazon, aimed at a better characterization of the chromosomes of these species. To obtain mitotic chromosomes, lymphocytes were grown in a culture medium for karyotypes (RPMI), and harvested cells were treated to obtain metaphase chromosomes. The results showed the karyotypic number for P. sextuberculata and P. expansa to be 2n = 28 chromosomes; in both species the karyotypes included 5 pairs of macrochromosomes and 9 pairs of microchromosomes, that is, 16m + 2sm + 10a and NF = 46. Visualization of the nucleolar organizing region (NOR) in these two species was obtained by silver nitrate staining, and provided evidence of a simple NOR in the pericentromeric region of the fi rst chromosomal pair. The diploid number was found to be the same as that described in the literature but NOR data are described for the fi rst time.
Recently, a bacterium strain of Ideonella sakaiensis was identified with the uncommon ability to degrade the poly(ethylene terephthalate) (PET). The PETase from I. sakaiensis strain 201-F6 catalyzes the hydrolysis of PET converting it to mono(2-hydroxyethyl) terephthalic acid (MHET), bis(2-hydroxyethyl)-TPA (BHET), and terephthalic acid (TPA). Despite the potential of this enzyme for mitigation or elimination of environmental contaminants, one of the limitations of the use of PETase for PET degradation is the fact that it acts only at moderate temperature due to its low thermal stability. Besides, molecular details of the main interaction of PET in the active site of PETase remains unclear. Herein, molecular docking and molecular dynamics (MD) simulations were applied to analyze structural changes of PETase induced by PET binding. Results from the essential dynamics revealed that β1-β2 connecting loop is very flexible. This Loop is located far from the active site of PETase and we suggest that it can be considered for mutagenesis in order to increase the thermal stability of PETase. The free energy landscape (FEL) demonstrates that the main change in the transition between the unbounded to the bounded state is associated with β7-α5 connecting loop, where the catalytic residue Asp206 is located. Overall, the present study provides insights into the molecular binding mechanism of PET into the PETase structure and a computational strategy for mapping flexible regions of this enzyme, which can be useful for the engineering of more efficient enzymes for recycling the plastic polymers using biological systems.
Contents of this paper were reviewed by the Technical Committee of the 16 th International Congress of the Brazilian Geophysical Society and do not necessarily represent any position of the SBGf, its officers or members. Electronic reproduction or storage of any part of this paper for commercial purposes without the written consent of the Brazilian Geophysical Society is prohibited.
Purpose. The purpose of the study was to present a theoretical framework for the concept of attitude and to examine the attitudes of selected subjects within this frame of reference. It was hoped that the results would clarify the concept of "attitude” and that they would provide solutions for problems in education. Method. A theoretical framework which consisted of sixteen propositions dealing with organization, structure, function, and change of attitudes was presented as the frame of reference. The 180 subjects who responded to the questionnaire that was prepared for this study were selected f±om the student body of Andrews University, Michigan. They included male and female students in the first and third years of college and in graduate school. They responded to attitude statements which measured the affective, the cognitive, and the action components of their attitudes toward national defense, politics, and religion. The scores were used to determine component loadings and the intercorrelations between the components. These were used to locate the attitude objects in the attitude space, to draw the attitude structures, and to examine attitude changes. Eleven hypotheses were formulated. The first four hypotheses dealt with the usefulness of the framework and formed the first part of the analysis of the data. They dealt with the organization of attitudes, the hierarchical order of the components, and the role of arousal in attitude study. The remaining hypotheses considered the differences in subject groups, in terms of the theoretical frame of reference, and formed the second part of the analysis of the data. Results. The following results were obtained: 1. The organization of attitudes toward religion is not more consistent than attitudes toward the other two areas. 2. The attitude components are hierarchical. 3 . Attitudes of subjects who have aroused attitudes are better organized than those in groups with non-aroused attitudes. 4. The arousal scores in related eureas correlate with each other. 5. The value profiles of the subjects are very similar. 6. Female subjects' attitudes tend tc be mere expressive than males'. 7. Male subjects' attitudes are more instrumental than those of female subjects. 8. The attitudes of graduate students toward religion are more positive than those of students in the college levels. 9. There is no difference between males and females in the degree of positiveness in attitudes toward national defense and politics. 10. There is no difference in males' and females' attitudes toward religion. 11. The various attitude areas have a higher correlation in the groups of college students than in the groups of graduate students. Conclusions. The theoretical framework proved useful in the study of attitudes. It permitted the investigator to gather information about structures of attitudes ; structural changes ; differences in attitude structures between groups; and the relationships between different attitude components. This information can be useful in clarifying the concept of "attitude" and in finding solutions to problems in education, the behavioral sciences, and so forth.
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