Gemdimethyl Peptide Nucleic Acids (α/ß/γ-gdm-PNA): E/Z-Rotamers Influence the Selectivity in the Formation of Parallel/Antiparallel gdm-PNA:DNA/RNA Duplexes.

Peptide nucleic acids (PNAs) consist of an aminoethylglycine (aeg) backbone to which the nucleobases are linked through a tertiary amide group and bind to complementary DNA/RNA in a sequence-specific manner. The flexible aeg backbone has been the target for several chemical modifications of the PNA to improve its properties such as specificity, solubility, etc. PNA monomers exhibit a mixture of two rotamers (Z/E) arising from the restricted rotation around the tertiary amide N-CO bond. We have recently demonstrated that achiral gemdimethyl substitution at the α, ß, and γ sites on the aeg backbone induces exclusive Z (α-gdm)- or E-rotamer (ß-gdm) selectivity at the monomer level. It is now shown that γ/ß-gdm-PNA:DNA parallel duplexes are more stable than the analogous antiparallel duplexes, while γ/ß-gdm-PNA:RNA antiparallel duplexes are more stable than parallel duplexes. Furthermore, the γ/ß-gdm-PNA:RNA duplexes are more stable than the γ/ß-gdm-PNA:DNA duplexes. These results with γ/ß-gdm-PNA are the reverse of those previously seen with α-gdm-PNA oligomers that stabilized antiparallel α-gdm-PNA:DNA duplexes compared to α-gdm-PNA:RNA duplexes. The stability of antiparallel/parallel PNA:DNA/RNA duplexes is correlated with the preference for Z/E-rotamer selectivity in α/ß-gdm-PNA monomers, with Z-rotamers (α-gdm) leading to antiparallel duplexes and E-rotamers (ß/γ-gdm) leading to parallel duplexes. The results highlight the role and importance of Z- and E-rotamers in controlling the structural preferences of PNA:DNA/RNA duplexes.

A Prospective Study to Correlate Difficult Intubation with Difficult Laryngeal Exposure for Microlaryngeal Surgery using Various Grading Scales of Difficult Intubation.

Adequate visualization of the vocal folds is essential for optimal phonosurgery. Pre-operative knowledge of a difficult laryngeal exposure (DLE) can alert the surgeon regarding the need for alternative measures. Our study is based on the hypothesis that a patient who has difficult intubation (DI) is likely to have DLE, thus scales anticipating DI should also anticipate DLE. Our aims were to correlate patients of actual DI on table with patients who had DLE, secondly to assess the ability of grading scales of DI to predict DLE and finally to obtain a cut-off value of neck circumference and length for predicting DLE. This is a prospective, observational study wherein four grading scales; Modified Mallampati Classification (MMC), 3-3-2, Upper lip bite test (ULBT) and Neck Mobility (NM) were used for anticipating DI and correlated with DLE during MLS. Occurrence of actual DI and DLE was correlated. Neck circumference and neck length was correlated with incidence of DLE. Out of 42 patients, 22 were anticipated to have DI (52.38%). Actual incidence of DI was 6 (14.28%) and DLE was 10 (23.80%). Correlation between actual DI and DLE was statistically significant. Of the 4 grading scales, ULBT was significant in predicting DLE. Neck circumference more than 37.5 cm and neck length less than 15.3 cm was significant in anticipating DLE. There is a significant correlation between DI and DLE. A positive ULBT, neck circumference more than 37.5 cms and neck length less than 15.3 cms are independently suggestive of a DLE.

Gem-dimethyl peptide nucleic acid (α/ß/γ-gdm-PNA) monomers: synthesis and the role of gdm-substituents in preferential stabilisation of Z/E-rotamers.

The flexible backbone of aminoethylglycine (aeg) PNA upon substitution becomes sterically constrained to enable conformational pre-organization for preferential binding to DNA or RNA. The bulky gem-dimethyl (gdm) substituent on carbons adjacent to the t-amide sidechain either at Cα (glycyl) or Cß/Cγ (aminoethylene) sides may influence the Z/E rotamer ratio arising from a restricted rotation around the t-amide bond. Employing 2D NMR (NOESY), it is shown here that the Cα-gdm-PNA-T monomer exhibits exclusively the Z-rotamer, while the Cß-gdm-PNA-T monomer shows only the E-rotamer. The unsubstituted aeg-PNA-T and Cγ-gdm-PNA-T monomers display a mixture of Z/E rotamers. The rotamers with t-amide carbonyl pointing towards the gem-dimethyl group always prevailed. The results are supported by computational studies that suggested that the preferred rotamers are the outcome of a net energetic benefit from the stabilising n-π* interactions of carbonyls (amide backbone and t-amide sidechain), and C-HO interactions and the destabilising steric clash of gem-dimethyl groups with the t-amido methylene group. The E-rotamer structure in Cγ-gdm is also characterised by X-ray crystallography. The exclusive E-rotamer for the Cß-gdm monomer seen in solution here is the first such example among several modified PNA monomers. Since the conformation of the sidechain is important for inducing base stacking and effective base pairing, the exclusive E-rotamer in the Cß-gdm monomer may have significance in the properties of the derived PNA : DNA/RNA duplexes with all E-rotamers.

Landmark Papers on Blood and Component Transfusion Therapy in the Critically Ill: A Critical Analysis.

How to cite this article: Khasne RW, Kulkarni PA, Kulkarni AP. Landmark Papers on Blood and Component Transfusion Therapy in the Critically Ill: A Critical Analysis. Indian J Crit Care Med 2019;23(Suppl 3):S207-S211.

Nitrophenol removal by simultaneous nitrification denitrification (SND) using T. pantotropha in sequencing batch reactors (SBR).

Nitrophenol removal was assessed using four identical lab scale sequencing batch reactors R (background control), R1 (4-nitrophenol i.e. 4-NP), R2 (2,4-dinitrophenol i.e. 2,4-DNP), and R3 (2,4,6-trinitrophenol i.e. 2,4,6-TNP). In the present study, the SND based SBR system was used to carry out total nitrogen removal at reduced aeration (DO=2mg/L) using a specifically designed single sludge biomass containing Thiosphaera pantotropha. The concentration of each of the nitrophenols was gradually increased from 2.5 to 200mg/L during acclimation. The nitrophenols were used as the sole source of nitrogen during study. A synthetic feed was designed to direct SND in the bioreactors. It was observed that overall removal for 4-NP was 98% and for 2,4-DNP and 2,4,6 TNP, removals varied between 83% and 84%. The COD removal for 4-NP was 99% and for 2,4-DNP and 2,4,6-TNP was 97-98% during acclimation. Total nitrogen and nitrophenol removals were achieved via SND.

Buckminsterfullerene's (C60) octanol-water partition coefficient (Kow) and aqueous solubility.

To assess the risk and fate of fullerene C60 in the environment, its water solubility and partition coefficients in various systems are useful. In this study, the log Kow of C60 was measured to be 6.67, and the toluene-water partition coefficient was measured at log Ktw = 8.44. From these values and the respective solubilities of C60 in water-saturated octanol and water-saturated toluene, C60's aqueous solubility was calculated at 7.96 ng/L(1.11 x 10(-11) M) for the organic solvent-saturated aqueous phase. Additionally, the solubility of C60 was measured in mixtures of ethanol-water and tetrahydrofuran-water and modeled with Wohl's equation to confirm the accuracy of the calculated solubility value. Results of a generator column experiment strongly support the hypothesis that clusters form at aqueous concentrations below or near this calculated solubility. The Kow value is compared to those of other hydrophobic organic compounds, and bioconcentration factors for C60 were estimated on the basis of Kow.

Solubility of C60 in solvent mixtures.

The potential large-scale production of fullerene C60 and its widespread use in consumer products may translate into occupational and public exposure and in long-term environmental exposure. To assess the risk and fate of C60 in the environment, it is important to understand its solvate formation in common industrial solvents as the solvates may affect various properties of C60 including reactivity and toxicity, particularly when solvates occur in C60 clusters. In this study, the solubility measurements in mixed solvent system can provide useful information about solvate formation. The solubility of C60 was measured in pure toluene, tetrahydrofuran, ethanol, and acetonitrile to be 3000, 11, 1.4, and 0.04 mg/L, respectively. Additionally, the solubility of C60 was measured in mixtures of toluene-acetonitrile, toluene-ethanol, toluene-tetrahydrofuran, and acetonitrile-tetrahydrofuran. The solubility data were modeled with some accuracy using Wohl's equation. The estimated crystal energy term for C60 in tetrahydrofuran was different than that in the other solvents, indicating that the C60 solid phase in equilibrium with tetrahydrofuran solution may be a solvated crystal.