Energetic Diversity in the Electron-Transfer Pathways of Type I Photosynthetic Reaction Centers.

Photosynthetic reaction centers from heliobacteria (HbRC) and green sulfur bacteria (GsbRC) are homodimeric proteins and share a common ancestor with photosystem I (PSI), classified as type I reaction centers. Using the HbRC crystal structure, we calculated the redox potential (Em) values in the electron-transfer branches, solving the linear Poisson-Boltzmann equation and considering the protonation states of all titratable sites in the entire protein-pigment complex. Em(A-1) for bacteriochlorophyll g at the secondary site in HbRC (-1157 mV) is as low as Em(A-1) for chlorophyll a in PSI (-1173 mV). Em(A0/HbRC) is at the same level as Em(A0/GsbRC) and is 200 mV higher than Em(A0/PSI) due to the replacement of PsaA-Trp697/PsaB-Trp677 in PSI with PshA-Arg554 in HbRC. In contrast, Em(FX) for the Fe4S4 cluster in HbRC (-420 mV) is significantly higher than Em(FX) in GsbRC (-719 mV) and PSI (-705 mV) due to the absence of acidic residues that correspond to PscA-Asp634 in GsbRC and PsaB-Asp575 in PSI. It seems likely that type I reaction centers have evolved, adopting (bacterio)chlorophylls suitable for their light environments while maintaining electron-transfer cascades.

Energetics of the Electron Transfer Pathways in the Homodimeric Photosynthetic Reaction Center.

Photosynthetic reaction centers from a green sulfur bacterium (GsbRC), the PscA/PscA proteins, and photosystem I (PSI), PsaA/PsaB proteins, share structural similarities. Here, we report the redox potential (Em) values of GsbRC by solving the linear Poisson-Boltzmann equation and considering the protonation states of all titratable sites in the entire GsbRC protein and identify the factors that shift the Em values with respect to PSI. The Em values for one-electron reduction of the accessory (A-1) and adjacent (A0) chlorophylls in GsbRC are 100-250 mV higher than those in PSI, whereas the Em values for the Fe4S4 cluster (FX) are at the same level. The PsaA-Trp697/PsaB-Trp677 pair in PSI, which forms the A1-quinone binding site, is replaced with PscA-Arg638 in GsbRC. PsaB-Asp575 in PSI, which is responsible for the Em difference between A1A and A1B quinones in PSI, is absent in GsbRC. These discrepancies also contribute to the upshift in Em(A-1) and Em(A0) in GsbRC with respect to PSI. It seems likely that the upshifted Em for chlorophylls in GsbRC ultimately originates from the characteristics of the electrostatic environment that corresponds to the A1 site of PSI.

[Laparoscopic Gastrectomy for Gastric Cancer with Adachi Type â ¥ Vascular Anomaly-A Case Report].

We report a case of laparoscopic gastrectomy for gastric cancer with an anomalous celiac trunk categorized as Type Ⅵ- Group 24 in the Adachi classification. Upper gastrointestinal endoscopy in an 81-year-old male revealed a shallow depressed lesion in the middle of the gastric body. Close examination led to diagnosis of cT1bN0M0, cStage Ⅰ gastric cancer, and laparoscopic distal gastrectomy was planned. Contrast-enhanced CT revealed no anomalous bifurcation of the hepatic artery, but the common hepatic artery ran on the dorsal side of the portal vein, branching from the superior mesenteric artery. Therefore, an Adachi Type Ⅵ-Group 24 celiac trunk anomaly was diagnosed. During surgery, the common hepatic artery could not be confirmed in guiding suprapancreatic lymph node dissection, and the portal vein was exposed. Anterior to the portal vein, nerves that are usually around the common hepatic artery continuously ran toward the hepatoduodenal ligament instead. Suprapancreatic lymph nodes were dissected, with the portal vein considered as the common hepatic artery. Adachi Type Ⅵ is a rare anomaly with an incidence of about 2%. Preoperative diagnosis enables safe and appropriate lymph node dissection.

Redox Potentials of Iron-Sulfur Clusters in Type I Photosynthetic Reaction Centers.

The electron transfer pathways in type I photosynthetic reaction centers, such as photosystem I (PSI) and reaction centers from green sulfur bacteria (GsbRC), are terminated by two Fe4S4 clusters, FA and FB. The protein structures are the basis of understanding how the protein electrostatic environment interacts with the Fe4S4 clusters and facilitates electron transfer. Using the protein structures, we calculated the redox potential (Em) values for FA and FB in PSI and GsbRC, solving the linear Poisson-Boltzmann equation. The FA-to-FB electron transfer is energetically downhill in the cyanobacterial PSI structure, while it is isoenergetic in the plant PSI structure. The discrepancy arises from differences in the electrostatic influences of conserved residues, including PsaC-Lys51 and PsaC-Arg52, located near FA. The FA-to-FB electron transfer is slightly downhill in the GsbRC structure. Em(FA) and Em(FB) exhibit similar levels upon isolation of the membrane-extrinsic PsaC and PscB subunits from the PSI and GsbRC reaction centers, respectively. The binding of the membrane-extrinsic subunit at the heterodimeric/homodimeric reaction center plays a key role in tuning Em(FA) and Em(FB).

Abdominal compartment syndrome secondary to a large retroperitoneal hematoma caused by ruptured gastroduodenal artery pseudoaneurysms in a patient with severe acute pancreatitis.

Background: Abdominal compartment syndrome (ACS) is a known complication of severe acute pancreatitis. It is typically secondary to visceral edema and aggressive fluid resuscitation, but rarely caused by a retroperitoneal hematoma due to ruptured visceral pseudoaneurysms. Case Presentation: A 49-year-old man presented in shock with a history of heavy alcohol use and was transferred to the intensive care unit with a diagnosis of severe acute pancreatitis. Computed tomography scan on hospital day 2 revealed a large retroperitoneal hematoma due to ruptured gastroduodenal artery pseudoaneurysms. Despite adequate resuscitation, the patient developed ACS, which required decompressive laparotomy on hospital day 10. Open abdominal management was continued until multiorgan failure resolved. He was eventually discharged to a rehabilitation hospital 3 months after presenting. Conclusion: We report a patient with severe acute pancreatitis who underwent decompressive laparotomy for ACS secondary to a large retroperitoneal hematoma due to ruptured gastroduodenal artery pseudoaneurysms.

Possible Association between Recurrent Chronic Subdural Hematoma and Dural Arteriovenous Fistula: A Case Report with Three-dimensional Fusion Images.

Several studies have reported the coexistence of chronic subdural hematoma (CSDH) and dural arteriovenous fistula (DAVF); however, the association between these two entities remains unknown. A case of coexisting CSDH and DAVF that was successfully treated with burr hole surgery and middle meningeal artery (MMA) embolization is reported herein. We visualized the positional relationship between CSDH and DAVF by fusion three-dimensional computer graphics images reconstructed from multimodal imaging studies, which revealed that the shunt point of the DAVF was far from the burr hole and was in contact with the CSDH membrane at the center of the CSDH. Additionally, the chronological development of CSDH in the presence of DAVF and the complete disappearance of both DAVF and CSDH after MMA embolization were also demonstrated. This study suggests a possible association between recurrent CSDH and DAVF.

Mechanism of Mixed-Valence Fe2.5+···Fe2.5+ Formation in Fe4S4 Clusters in the Ferredoxin Binding Motif.

Most low-potential Fe4S4 clusters exist in the conserved binding sequence CxxCxxC (CnCn+3Cn+6). Fe(II) and Fe(III) at the first (Cn) and third (Cn+6) cysteine ligand sites form a mixed-valence Fe2.5+···Fe2.5+ pair in the reduced Fe(II)3Fe(III) cluster. Here, we investigate the mechanism of how the conserved protein environment induces mixed-valence pair formation in the Fe4S4 clusters, FX, FA, and FB in photosystem I, using a quantum mechanical/molecular mechanical approach. Exchange coupling between Fe sites is predominantly determined by the shape of the Fe4S4 cluster, which is stabilized by the preorganized protein electrostatic environment. The backbone NH and CO groups in the conserved CxxCxxC and adjacent helix regions orient along the FeCn···FeC(n+6) axis, generating an electric field and stabilizing the FeCn(II)FeC(n+6)(III) state in FA and FB. The overlap of the d orbitals via -S- (superexchange) is observed for the single FeCn(II)···FeC(n+6)(III) pair, leading to the formation of the mixed-valence Fe2.5+···Fe2.5+ pair. In contrast, several superexchange Fe(II)···Fe(III) pairs are observed in FX due to the highly symmetric pair of the CDGPGRGGTC sequences. This is likely the origin of FX serving as an electron acceptor in the two electron transfer branches.

Electron Acceptor-Donor Iron Sites in the Iron-Sulfur Cluster of Photosynthetic Electron-Transfer Pathways.

In photosystem I, two electron-transfer pathways via quinones (A1A and A1B) are merged at the iron-sulfur Fe4S4 cluster FX into a single pathway toward the other two Fe4S4 clusters FA and FB. Using a quantum mechanical/molecular mechanical approach, we identify the redox-active Fe sites in the clusters. In FA and FB, the Fe site, which does not belong to the CxxCxxCxxxCP motif, serves as an electron acceptor/donor. FX has two independent electron acceptor Fe sites for A- and B-branch electron transfers, depending on the Asp-B575 protonation state, which causes the A1A-to-FX electron transfer to be uphill and the A1B-to-FX electron transfer to be downhill. The two asymmetric electron-transfer pathways from A1 to FX and the separation of the electron acceptor and donor Fe sites are likely associated with the specific role of FX in merging the two electron transfer pathways into the single pathway.

Compact megajoule-class pulsed power supply for generating long-pulsed magnetic fields.

A pulsed power supply with a compact and low-cost electric-double-layer-capacitor (EDLC) is developed for generating pulsed magnetic fields with a long pulse duration of a few seconds. The system is demonstrated in three experimental setups using a 10.7 F- or 50 F-EDLC capacitor bank. By using the 10.7 F-EDLC capacitor bank with a 27 mm wide-bore magnet, the pulsed magnetic field with a peak field strength of 24.3 T and a pulse duration of ∼1 s is generated. The field profiles are reproduced in the theoretical calculations taking Joule heating into account. The calculations are also used to discuss possible variations of the field profile for future investigations.