Methods to functionalize gold nanoparticles with tandem-phosphorothioate DNA: role of physicochemical properties of the phosphorothioate backbone in DNA adsorption to gold nanoparticles.

Perception of the differences in the physicochemical properties of phosphorothioate DNA (PS-DNA) and phosphodiester DNA (PO-DNA) greatly aids in understanding the AuNP-DNA binding process. Replacing one non-bridging oxygen atom of the anionic phosphodiester backbone with a sulfur atom leads to a major change in the DNA adsorption mechanism of AuNPs. In this work, we investigated and compared salt-aging, low pH-assisted, and freeze-thaw methods for conjugating phosphorothioate-modified oligonucleotides to AuNPs. The results obtained clearly demonstrate that only the pH-assisted method can successfully bind tandem phosphorothioate DNA to gold nanoparticles and sufficiently maintain the colloidal stability of AuNPs. When a phosphate group is converted to a phosphorothioate group, the negative charge of the phosphate group is located on the sulfur atom. Due to the soft nature of sulfur (a very weak H-bond acceptor), the negative charge on the sulfur atom cannot be shielded even with the gradual addition of salt to increase the ionic strength, so, the pH-assisted based method is the best for the functionalization of AuNPs with tandem-PS DNA.

Probing the mechanical properties of ORF3a protein, a transmembrane channel of SARS-CoV-2 virus: Molecular dynamics study.

SARS-CoV-2-encoded accessory protein ORF3a was found to be a conserved coronavirus protein that shows crucial roles in apoptosis in cells as well as in virus release and replications. To complete the knowledge and identify the unknown of this protein, further comprehensive research is needed to clarify the leading role of ORF3a in the functioning of the coronavirus. One of the efficient approaches to determining the functionality of this protein is to investigate the mechanical properties and study its structural dynamics in the presence of physical stimuli. Herein, performing all-atom steered molecular dynamics (SMD) simulations, the mechanical properties of the force-bearing components of the ORF3a channel are calculated in different physiological conditions. As variations occurring in ORF3a may lead to alteration in protein structure and function, the G49V mutation was also simulated to clarify the relationship between the mechanical properties and chemical stability of the protein by comparing the behavior of the wild-type and mutant Orf3a. From a physiological conditions point of view, it was observed that in the solvated system, the presence of water molecules reduces Young's modulus of TM1 by ∼30 %. Our results also show that by substitution of Gly49 with valine, Young's modulus of the whole helix increases from 1.61 ± 0.20 to 2.08 ± 0.15 GPa, which is consistent with the calculated difference in free energy of wild-type and mutant helices. In addition to finding a way to fight against Covid-19 disease, understanding the mechanical behavior of these biological nanochannels can lead to the development of the potential applications of the ORF3a protein channel, such as tunable nanovalves in smart drug delivery systems, nanofilters in the new generation of desalination systems, and promising applications in DNA sequencing.

Hairpin-Spherical Nucleic Acids for Diagnosing COVID-19: a Simple Method to Generalize the Conventional PCR for Molecular Assays.

The COVID-19 pandemic revealed during the first global wave of this infectious disease that mass diagnostic testing was necessary to more rapidly detect infection in patients and control the pandemic. Therefore, extra research efforts to develop reliable and more accessible techniques for disease diagnosis are of supreme importance. Here, a target-responsive assembly of gold nanoparticle-core hairpin-spherical nucleic acids (AuNP-core H-SNAs) was implemented to modify the conventional polymerase chain reaction (PCR) assay for the "naked-eye" colorimetric detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA. Two hairpin DNA ligands are designed based on the two highly conserved regions within N and E genes of SARS-CoV-2 RNA by positioning two short palindromic arms (stem) on either side of a recognition sequence (loop). In the presence of a sequence-specific probe (activator), hairpin DNAs anchored to the surface of AuNPs unfold and expose the palindromic ends to the DNA-directed assembly of AuNPs. The sequence of the activator probes was chosen to be identical to the TaqMan probe in a real-time reverse transcription PCR (RT-PCR) assay for specifically targeting the N and E genes of SARS-CoV-2 RNA. They may either be degraded by the 5'-exonuclease activity of DNA polymerase during PCR cycles or stay intact depending on the presence or absence of the target template in the sample, respectively. Post-addition of H-SNA solutions to the final PCR products of some preconfirmed clinical samples for COVID-19 generated naked-eye-observable red and blue colors for positive and negative cases, respectively, with similar sensitivity to that of the real-time RT-PCR method.

Conventional PCR assisted single-component assembly of spherical nucleic acids for simple colorimetric detection of SARS-CoV-2.

Continuous identification of suspected infectious cases is crucial to control the recent pandemic caused by the novel human coronavirus SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2). Real-time polymerase chain reaction (real-time PCR) technology cannot be implemented easily and in large scale in some communities due to lack of resources and infrastructures. Here, we report a simple colorimetric strategy derived from linker-based single-component assembly of gold nanoparticle-core spherical nucleic acids (AuNP-core SNAs) for visual detection of PCR products of SARS-CoV-2 ribonucleic acid (RNA) template. A palindromic linker is designed based on SARS-CoV-2 specific E gene to program the identical colloidal SNAs into large assemblies along with a distinct red-to-purple color change. The linker acts as a probe of SARS-CoV-2 RNA in conventional PCR reaction. In the presence of the correct template the palindromic linker, which is complementary to a short region within the target amplicon, is cleaved by 5'-exonuclease activity of deoxyribonucleic acid (DNA) polymerase. Cleavage of the palindromic linker during the amplification process inhibits the single-component assembly formation of SNAs. So, positive and negative viral samples produce simply red and purple colors in the post PCR colorimetric test, respectively. Evaluation of the samples obtained from cases with laboratory-confirmed SARS-CoV-2 infection revealed that our assay can rival with real-time PCR method in sensitivity.

A palindromic-based strategy for colorimetric detection of HIV-1 nucleic acid: Single-component assembly of gold nanoparticle-core spherical nucleic acids.

Gold nanoparticle-core spherical nucleic acids (AuNP core-SNAs), by virtue of the programmable nature of oligonucleotides, have yielded access to the innovative strategies for targeted biodiagnostics. Here, DNA-directed self-assembly of AuNP core-SNAs has been used to design a colorimetric method to sense HIV-1 viral nucleic acid. This strategy utilizes an oligonucleotide with sequence of 5'-untranslated region (5' UTR) of the HIV-1 RNA genome anchored on the surface of AuNPs and a complementary linker strand with a palindromic sequence tail. In the absence of HIV-1 target nucleic acid the complementary linker induces self-assembly of SNAs based on sequence symmetry in the free palindromic tail which can bridge two DNA double helices. While in the presence of the target DNA, due to linker-target duplex formation, the colloidal stability and the red color of the SNAs solution are preserved. Picomole amounts of target DNA can easily be detected with the naked eyes. A 95-mer synthetic DNA strand with the same sequence of HIV-1 viral RNA was utilized for positive control of HIV-1 RNA. The selectivity of the selected linker was satisfactory up to 90% match.

Health-promoting behaviors in nursing students: is it related to self-efficacy for health practices and academic achievement?

Background Nursing students play a role in promotion of public health as health promoters and professional care providers. Therefore, health-promoting behaviors in nursing students and their self-efficacy for health practices are important in providing better services to patients and clients. With regard to the importance of these factors in the academic progress of students, this study was conducted to examine the level of health-promoting behaviors among nursing students and its relationship with self-efficacy for health practices and academic achievement. Methods This descriptive and correlational study was conducted on 217 nursing students of a large university of medical sciences in the south of Iran in 2016. Data were collected using the Persian version of the health promotion lifestyle profile (HPLP II), self-rated abilities for health practices scale (SRAHPS) and the grade point average of the students (levels A, B, C). Results The mean health-promoting behaviors (2.48 ± 0.35) and self-efficacy for health practices of the students (2.55 ± 0.62) were moderate. The mean score of the students' academic achievement was at level B (16.02 ± 1.85). The health-promoting behaviors were significantly correlated with self-efficacy for health practices (r = 0.623, p < 0.0001) and academic achievement (r = 0.285, p < 0.0001). Moreover, self-efficacy for health practices was significantly correlated with academic achievement (r = 0.282, p < 0.0001). Conclusion The correlation between the health-promoting behaviors and health self-efficacy with academic achievement can be a good basis in devising health and educational programs for students. In planning for promoting academic achievement and health-promoting behaviors of students, it is essential to pay special attention to enhancement of self-efficacy for health practices.

Nurses' professional competency and organizational commitment: Is it important for human resource management?

BACKGROUND: Professional competency is a fundamental concept in nursing, which has a direct relationship with quality improvement of patient care and public health. Organizational commitment as a kind of affective attachment or sense of loyalty to the organization is an effective factor for professional competency. OBJECTIVE: This study was conducted to evaluate the nurses´ professional competency and their organizational commitment as well as the relationship between these two concepts. METHODS AND MATERIALS: This descriptive-analytic study was conducted at the hospitals affiliated with a University of Medical Sciences, in the southeast of Iran in 2016. The sample included 230 nurses who were selected using stratified random sampling. Data were gathered by three questionnaires including socio-demographic information, competency inventory for registered nurse (CIRN) and Allen Meyer's organizational commitment. RESULTS: Results showed that professional competency (Mean±SD: 2.82±0.53, range: 1.56-4.00) and organizational commitment (Mean±SD: 72.80±4.95, range: 58-81) of the nurses were at moderate levels. There was no statistically significant correlation between professional competency and organizational commitment (ρ = 0.02; p = 0.74). There were significant differences in professional competency based on marital status (p = 0.03) and work experience (p<0.001). CONCLUSION: The results highlighted that the nurses needed to be more competent and committed to their organizations. Developing professional competency and organizational commitment is vital, but not easy. This study suggests that human resource managers should pursue appropriate strategies to enhance the professional competency and organizational commitment of their nursing staff. It is necessary to conduct more comprehensive studies for exploring the status and gaps in the human resource management of healthcare in different cultures and contexts.

Prediction of muscle activation for an eye movement with finite element modeling.

In this paper, a 3D finite element (FE) modeling is employed in order to predict extraocular muscles' activation and investigate force coordination in various motions of the eye orbit. A continuum constitutive hyperelastic model is employed for material description in dynamic modeling of the extraocular muscles (EOMs). Two significant features of this model are accurate mass modeling with FE method and stimulating EOMs for motion through muscle activation parameter. In order to validate the eye model, a forward dynamics simulation of the eye motion is carried out by variation of the muscle activation. Furthermore, to realize muscle activation prediction in various eye motions, two different tracking-based inverse controllers are proposed. The performance of these two inverse controllers is investigated according to their resulted muscle force magnitude and muscle force coordination. The simulation results are compared with the available experimental data and the well-known existing neurological laws. The comparison authenticates both the validation and the prediction results.