Synthesis of self-aggregative zinc chlorophylls possessing polymerizable esters as a atable model compound for main light-harvesting antennas of green photosynthetic bacteria

Zinc bacteriochlorophyll-d derivatives possessing a polymerizable moiety at the 17-propionate were prepared as model compounds of natural occurring chlorophylls in the main peripheral antennas of green photosynthetic bacteria (chlorosomes). The synthetic compounds self-aggregated in nonpolar organic solvents as well as in the solid state to give large oligomers similar to chlorosomal J-aggregates. Such introduction of the polymerizable groups in the ester did not suppress the ability of self-aggregation

Contribution of histone N-terminal tails to the structure and stability of nucleosomes

AbstractHistones are the protein components of the nucleosome, which forms the basic architecture of eukaryotic chromatin. Histones H2A, H2B, H3, and H4 are composed of two common regions, the “histone fold” and the “histone tail”. Many efforts have been focused on the mechanisms by which the post-translational modifications of histone tails regulate the higher-order chromatin architecture. On the other hand, previous biochemical studies have suggested that histone tails also affect the structure and stability of the nucleosome core particle itself. However, the precise contributions of each histone tail are unclear. In the present study, we determined the crystal structures of four mutant nucleosomes, in which one of the four histones, H2A, H2B, H3, or H4, lacked the N-terminal tail. We found that the deletion of the H2B or H3 N-terminal tail affected histone–DNA interactions and substantially decreased nucleosome stability. These findings provide important information for understanding the complex roles of histone tails in regulating chromatin structure

Histone variant H2A.B-H2B dimers are spontaneously exchanged with canonical H2A-H2B in the nucleosome

精子形成に重要なヒストンによるDNAの新たな折りたたみを解明. 京都大学プレスリリース. 2021-02-22.H2A.B is an evolutionarily distant histone H2A variant that accumulates on DNA repair sites, DNA replication sites, and actively transcribing regions in genomes. In cells, H2A.B exchanges rapidly in chromatin, but the mechanism has remained enigmatic. In the present study, we found that the H2A.B-H2B dimer incorporated within the nucleosome exchanges with the canonical H2A-H2B dimer without assistance from additional factors, such as histone chaperones and nucleosome remodelers. High-speed atomic force microscopy revealed that the H2A.B nucleosome, but not the canonical H2A nucleosome, transiently forms an intermediate “open conformation”, in which two H2A.B-H2B dimers may be detached from the H3-H4 tetramer and bind to the DNA regions near the entry/exit sites. Mutational analyses revealed that the H2A.B C-terminal region is responsible for the adoption of the open conformation and the H2A.B-H2B exchange in the nucleosome. These findings provide mechanistic insights into the histone exchange of the H2A.B nucleosome

Nasopalatine duct cyst associated with dental implant treatment: A case report

AbstractMaxillary anterior implants are associated with the risk of nasopalatine canal damage. Here we present the case of a 37-year-old man who developed a nasopalatine duct cyst after maxillary implant placement. The patient received an implant 3 months after the extraction of a fractured maxillary right central incisor. At a maintenance visit 9 years after the procedure, he complained of swelling and mild pain in the palatal region of the implant. A panoramic radiograph and computed tomography (CT) scan revealed a large, well-circumscribed, periapical radiolucency surrounding the apical portion of the implant and extending to the nasopalatine duct. We removed the entire lesion without removing the implant. Histopathologic examination of the resected specimen revealed a nasopalatine duct cyst. Accidental contact with the nasopalatine canal during implant surgery may have led to the development of the nasopalatine duct cyst. Careful planning using a preoperative CT scan prior to implant placement may prevent such complications

A Case of Hb S/A -α-thalassemia Exhibiting Quadriplegia Due to Distal Renal Tubular Acidosis

A 46-year-old negro seaman who called at Port Mizushima, Kurashiki City, from West Africa on May 21, 1981 developed quadriplegia shortly after having taken a tablet of an antipyretic agent on the ship. At the Port Clinic in Mizushima, hypopotassemia was detected and Guillain Barre syndrome was suspected. Adrenocorticosteroids therapy was started, but he became dyspneic because of the progression of the paralysis up to the level of respiratory muscle. He was, therefore, transferred to our emergency center and hospitalized. On the sixth hospital day (May 27), clinical manifestations improved by intravenous administration of potassium. Diagnosis of distal renal tubular acidosis was entertained on the basis of the presence of metabolic acidosis, hypopotassemia and the absence of acidification of urine by short duration NH4C1 acid-loading test. The hematological studies revealed a combination of sickle cell trait (Hb S/A) with α-thalassemia trait. It is well known that sickle cell anemia (Hb S/S) occasionally causes secondary distal renal tubular acidosis. However, the occurrence of renal tubular acidosis in sickle cell trait (Hb S/A) and in α-thalassemia trait (αTh/A) has not yet been reported in the literature. It is therefore thought that our observation on this case will deserve special description as one of the possible clinical signs of sickle cell trait