Effects of photobiomodulation with different application parameters on injection pain in children: a randomized clinical trial.

Photobiomodulation (PBM) has gained increasing interest due to its effectiveness in pain reduction in various fields of dentistry. However, the number of studies evaluating the effect of PBM on injection pain in children is very limited. The aim of the study was to evaluate the efficacy of PBM with three different application parameters (doses) + topical anesthesia on reducing injection pain and to compare these results with the placebo PBM + topical anesthesia in children during supraperiosteal anesthesia administration. 160 children were randomly divided into 4 groups, 3 experimental and 1 control, with 40 subjects in each. In the experimental groups, before the anesthesia administration, PBM with a power of 0.3 W was applied for 20, 30 and 40 s in groups 1, 2 and 3, respectively. In group 4, a placebo application of laser was performed. The pain felt during the injection was assessed using the Wong-Baker Faces Pain Rating Scale (PRS), and also the Face, Legs, Activity, Cry, Consolability (FLACC) Scale. Statistical analyses were performed to evaluate the data (p < 0.05). The mean FLACC Scale pain scores were 3.02 ± 2.93, 2.92 ± 2.54, 2.12 ± 1.89 and 1.77 ± 1.90 for the placebo group, and Groups 1, 2, and 3, respectively. Furthermore, the mean PRS scores were 1 ± 1.03, 0.95 ± 0.98, 0.80 ± 0.822 and 0.65 ± 0.921 for the placebo group, and Groups 1, 2 and 3, respectively. The "no pain response" rate was higher in Group 3 as compared to Groups 1, 2, and placebo according to the FLACC Scale and PRS; however, no difference was found between the groups (p = 0.109, p = 0.317). Injection pain in children did not differ with placebo and PBM applied with a power of 0.3 W for 20, 30 and 40 s.

Heterologous expression, purification and structural features of native Dictyostelium discoideum dye-decolorizing peroxidase bound to a natively incorporated heme.

The Dictyostelium discoideum dye-decolorizing peroxidase (DdDyP) is a newly discovered peroxidase, which belongs to a unique class of heme peroxidase family that lacks homology to the known members of plant peroxidase superfamily. DdDyP catalyzes the H2O2-dependent oxidation of a wide-spectrum of substrates ranging from polycyclic dyes to lignin biomass, holding promise for potential industrial and biotechnological applications. To study the molecular mechanism of DdDyP, highly pure and functional protein with a natively incorporated heme is required, however, obtaining a functional DyP-type peroxidase with a natively bound heme is challenging and often requires addition of expensive biosynthesis precursors. Alternatively, a heme in vitro reconstitution approach followed by a chromatographic purification step to remove the excess heme is often used. Here, we show that expressing the DdDyP peroxidase in ×2 YT enriched medium at low temperature (20°C), without adding heme supplement or biosynthetic precursors, allows for a correct native incorporation of heme into the apo-protein, giving rise to a stable protein with a strong Soret peak at 402 nm. Further, we crystallized and determined the native structure of DdDyP at a resolution of 1.95 Å, which verifies the correct heme binding and its geometry. The structural analysis also reveals a binding of two water molecules at the distal site of heme plane bridging the catalytic residues (Arg239 and Asp149) of the GXXDG motif to the heme-Fe(III) via hydrogen bonds. Our results provide new insights into the geometry of native DdDyP active site and its implication on DyP catalysis.