We reviewed 275 cases and calculated the prevalence of bacteriologically or radiologically confirmed acute haematogenous osteomyelitis in children under 13 resident in Greater Glasgow during 1970 to 1990. In the 20-year period there was a fall of over 50%, mainly involving cases of long-bone infection, and those due to Staphylococcus aureus. There was a reduced incidence of complications. The proportion of cases involving long bones decreased from 84% to 57%, and those of Staphylococcus aureus infection from 55% to 31%. These changes, in what is becoming a rare disease, need to be known to ensure early diagnosis and adequate treatment, particularly of subacute non-staphylococcal infection at unusual sites.

A cytochrome P450 was engineered to selectively incorporate Ir(Me)-deuteroporphyrin IX (Ir(Me)-DPIX), in lieu of heme, in bacterial cells. Cofactor selectivity was altered by introducing mutations within the heme-binding pocket that discriminate the deuteroporphyrin macrocycle, in combination with mutations to the P450 axial cysteine to accommodate a pendant methyl group on the Ir(Me)-center. This artificial metalloenzyme was investigated for activity in non-native metallocarbenoid-mediated olefin cyclopropanation reactions and showed enhanced activity for aliphatic and electron-deficient olefins when compared to the native heme enzyme. This work provides a general strategy to augment the chemical functionality of heme enzymes in cells with application towards abiotic catalysis.

The linker histone H1 is the most abundant group of eukaryotic chromatin-binding proteins. The mechanism underlying the diverse physiological functions of H1 remains unclear. Here we used singlemolecule fluorescence and force microscopy to observe the behavior of H1 on DNA under different tensions. Unexpectedly, we found that H1 coalesces around nascent ssDNA. Molecular dynamics simulations revealed that multivalent and transient interactions between H1 and ssDNA mediate their phase separation. We further showed that longer and unpaired nucleic acids result in more viscous, gellike H1 droplets. Finally, we imaged H1 puncta in cells under normal and stressed conditions and observed that RPA and H1 occupy separate nuclear regions. Overall, our results provide a new perspective to understanding the role of H1 in genome organization and maintenance.

Biomolecular condensation constitutes an emerging mechanism for transcriptional regulation. Recent studies suggest that the co-condensation between transcription factors (TFs) and DNA can generate mechanical forces driving genome rearrangements. However, the reported forces generated by protein-DNA co-condensation are typically below one piconewton (pN), questioning its physiological significance. Moreover, the force-generating capacity of these condensates in the chromatin context remains unknown. Here, we show that Sox2, a nucleosome-binding pioneer TF, forms co-condensates with DNA and generates forces up to 7 pN, exerting considerable mechanical tension on DNA strands. We find that the disordered domains of Sox2 are required for maximum force generation but not for condensate formation. Furthermore, we show that nucleosomes dramatically attenuate the mechanical stress exerted by Sox2 by sequestering it from coalescing on bare DNA. Our findings reveal that TF-mediated DNA condensation can exert significant mechanical stress on the genome which can nonetheless be attenuated by the chromatin architecture.

No abstract