The Dynamic Effect of the Valleculae on Singing Voice - An Exploratory Study Using 3D Printed Vocal Tracts.

BACKGROUND AND OBJECTIVES: The valleculae can be seen as a pair of side branches of the human vocal tract like the piriform fossae. While the acoustic properties of the piriform fossae have been explored in detail, there is little evidence of full exploration of the acoustic properties of the valleculae. A recent investigation (Vampola, Horácek, & Svec, 2015), using a finite element model of a single vowel /a/, suggests that the valleculae created two antiresonances and two resonances in the high frequency region (above 4kHz) along with those produced by the piriform sinuses. In the current study, we investigate, in multiple vowels, the acoustic influences of the valleculae in singing voice, using 3-D printed vocal tracts. METHOD: MRI data were collected from an operatic tenor singing English vowels /a/, /u/, /i/. The images of each vowel were segmented and edited to create a pair of tracts, where one is the original and one had the valleculae digitally removed.The printed tracts were then placed atop a vocal tract organ loudspeaker, excited by white noise. Recordings were made with a microphone placed in front of the mouths of the tracts, to measure their frequency responses. RESULTS: Dimensional changes were observed in valleculae of different vowels, with the long-term average spectra of the recordings illustrating clear differences between the frequency responses of the va-nova (valleculae - no valleculae) pairs, which varies with vowels. CONCLUSION: The experiment demonstrates the dynamic1 nature of the shapes of the valleculae in the human vocal tract and its acoustic consequences. It provides evidence that the valleculae have similar acoustic properties to the piriform fossae but with larger variations, and in some cases can influence acoustically the frequency region below 4kHz. The results suggest that large volume valleculae have the potential to impede to some extent the acoustic effect of the singers formant cluster and small valleculae may do the reverse. Since the volume of the valleculae is observed to be largely dependent on tongue movement and also with changes to the uttered vowel, it can be assumed that the high frequency energy, including that within the singer's formant region, could be vowel dependent. Strategies to control valleculae volumes are likely to be highly relevant to voice pedagogy practice as well as singing performance.

One-Step Surface Modification to Graft DNA Codes on Paper: The Method, Mechanism, and Its Application.

Glass slides have been widely used for DNA immobilization in DNA microarray and numerous bioassays for decades, whereas they are faced with limitations of low probe density, time-consuming modification steps, and expensive instruments. In this work, a simple one-step surface modification method using 3-aminopropyl trimethoxysilane (APTMS) has been developed and applied to graft DNA codes on paper. Higher DNA immobilization efficiency was obtained in comparison with that in a conventional method using glass slides. Fluorescence detection, X-ray photoelectron spectroscopy (XPS), infrared spectra (FT-IR), and pH influence studies were employed to characterize the surface modification and subsequent DNA immobilization, which further reveals a mechanism in which this method lies in ionic interactions between the positively charged APTMS-modified paper surface and negatively charged DNA probes. Furthermore, an APTMS-modified paper-based device has been developed to demonstrate application in low-cost detection of a foodborne pathogen, Giardia lamblia, with high sensitivity (the detection limit of 22 nM) and high specificity. Compared with conventional methods using redundant cross-linking reactions, our method is simpler, faster, versatile, and lower-cost, enabling broad applications of paper-based bioassays especially for point-of-care detection in resource-poor settings.

Enhancing Catalytic Activity of Uranyl-Dependent DNAzyme by Flexible Linker Insertion for More Sensitive Detection of Uranyl Ion.

The uranyl-dependent DNAzyme 39E cleaves its nucleic acid substrate in the presence of uranyl ion (UO22+). It has been widely utilized in many sensor designs for selective and sensitive detection of UO22+ in the environment and inside live cells. In this work, by inserting a flexible linker (C3 Spacer) into one critical site (A20) of the 39E catalytic core, we successfully enhanced the original catalytic activity of 39E up to 8.1-fold at low UO22+ concentrations. Applying such a modified DNAzyme (39E-A20-C3) in a label-free fluorescent sensor for UO22+ detection achieved more than 1 order of magnitude sensitivity enhancement over using native 39E, with the UO22+ detection limit improved from 2.6 nM (0.63 ppb) to 0.19 nM (0.047 ppb), while the high selectivity to UO22+ over other metal ions was fully preserved. The method was also successfully applied for the detection of UO22+-spiked environmental water samples to demonstrate its practical usefulness.

Photocaged G-Quadruplex DNAzyme and Aptamer by Post-Synthetic Modification on Phosphodiester Backbone.

G-quadruplex-containing DNAzymes and aptamers are widely applied in many research fields because of their high stability and prominent activities versus the protein counterparts. In this work, G-quadruplex DNAs were equipped with photolabile groups to construct photocaged DNAzymes and aptamers. We incorporated TEEP-OH (thioether-enol phosphate, phenol substituted) into phosphodiester backbone of G-quadruplex DNA by a facile post-synthetic method to achieve efficient photocaging of their activities. Upon light irradiation, the peroxidase-mimicking activity of the caged G-quadruplex DNAzyme was activated, through the transformation of TEEP-OH into a native DNA phosphodiester without any artificial scar. Similarly, the caged G-quadruplex thrombin-binding aptamer also showed light-induced activation of thrombin inhibition activity. This method could serve as a general strategy to prepare photocaged G-quadruplex DNA with other activities for noninvasive control of their functions.

Cationic Peptide Conjugation Enhances the Activity of Peroxidase-Mimicking DNAzymes.

Peroxidase-mimicking DNAzymes containing G-quadruplex structures are widely applied in chemistry as catalysts and signal amplification for biosensing. Enhancing the catalytic activity of these DNAzymes can therefore improve the performance of many catalysts and biosensors using them. In this work, we synthesized cationic peptide conjugates of peroxidase-mimicking DNAzymes, which were found to exhibit both enhanced peroxidase and oxidase activities up to 4-fold and 3-fold compared with the original DNAzymes, respectively. Further investigation suggested that the enhanced activity was ascribed to the stabilization of parallel DNA G-quadruplex structures and hemin binding by the cationic peptide covalently attached to the DNAzyme. Such a mechanism of activity enhancement was successfully utilized for biosensing applications with improved sensitivity and broadened target range. Hydrogen peroxide (H2O2) detection in K(+)-free solutions by the DNAzyme-peptide conjugate showed 2-fold sensitivity enhancement over the unmodified DNAzyme under the same condition, and the activity switch by target-induced cleavage of the DNAzyme-peptide conjugate was also used for the detection of caspase 3 protease with enzymatic amplification in homogeneous solutions.

Postsynthetic Modification of DNA Phosphodiester Backbone for Photocaged DNAzyme.

Photocaged (photoactivatable) biomolecules are powerful tools for noninvasive control of biochemical activities by light irradiation. DNAzymes (deoxyribozymes) are single-stranded oligonucleotides with a broad range of enzymatic activities. In this work, to construct photocaged DNAzymes, we developed a facile and mild postsynthetic method to incorporate an interesting photolabile modification (thioether-enol phosphate, phenol substituted, TEEP-OH) into readily available phosphorothioate DNA. Upon light irradiation, TEEP-OH transformed into a native DNA phosphodiester, and accordingly the DNAzymes with RNA-cleaving activities were turned "on" from its inactive and caged form. Activation of the TEEP-OH-caged DNAzyme by light was also successful inside live cells.