SOLUTION PROPERTIES OF ANTITUMOR CARBOXYMETHYLATED DERIVATIVES OF α-(1→3)-D-GLUCAN FROM GANODERMA LUCIDUM

Fractions of a water insoluble α-(1→3)-D-glucan (GL) extracted from Ganoderma lucidum were carboxy-methylated (CM) to obtain water-soluble carboxymethylated derivatives (CM-GL) having a degree of substitution (DS) of0.38～0.51. Weight-average molecular weight M_w and intrinsic viscosity [η] of the samples CM-GL were measured by gelpermeation chromatography combined with laser light scattering (GPC-LLS) and viscometry. The CM-GL exhibits a stifferchain in aqueous solution at 25℃ than the original glucan, The antitumor activities against Ehrlich ascites carcinoma (EAC,5×10~6) of the carboxymethylated derivatives from the α-glucan and curdlan, a β-glucan, are significantly higher than thoseof the original glucans. The effects of the relatively low molecular weight, expanded chains and better water-solubility of theCM-GL on the enhancement of antitumor activity could not be neglected. The chain stiffness decreased speedily withincrease of temperature from 40 to 60℃ or NaOH concentration from 0.1 to 0.4 in the solution, respectively, and the changeof the chain stiffness is reversible.

Cryo-electron microscopy structure of the intact photosynthetic light-harvesting antenna-reaction center complex from a green sulfur bacterium

The photosynthetic reaction center complex(RCC)of green sulfur bacteria(GSB)consists of the membrane-imbedded RC core and the peripheric energy transmitting proteins called Fenna–Matthews–Olson(FMO).Functionally,FMO transfers the absorbed energy from a huge peripheral light-harvesting antenna named chlorosome to the RC core where charge separation occurs.In vivo,one RC was found to bind two FMOs,however,the intact structure of RCC as well as the energy transfer mechanism within RCC remain to be clarified.Here we report a structure of intact RCC which contains a RC core and two FMO trimers from a thermophilic green sulfur bacterium Chlorobaculum tepidum at 2.9A resolution by cryo-electron microscopy.The second FMO trimer is attached at the cytoplasmic side asymmetrically relative to the first FMO trimer reported previously.We also observed two new subunits(PscE and PscF)and the N-terminal transmembrane domain of a cytochrome-containing subunit(PscC)in the structure.These two novel subunits possibly function to facilitate the binding of FMOs to RC core and to stabilize the whole complex.A new bacteriochlorophyll(numbered as 816)was identified at the interspace between PscF and PscA-1,causing an asymmetrical energy transfer from the two FMO trimers to RC core.Based on the structure,we propose an energy transfer network within this photosynthetic apparatus.

Survival nomograms for simultaneous resection of primary and hepatic lesions without neoadjuvant chemotherapy in patients with resectable colorectal liver metastasis

Background No well-performing nomogram has been developed specifically to predict individual-patient cancer-specific survival(CSS)and overall survival(OS)among patients with resectable colorectal liver metastasis(CRLM)who undergo simultaneous resection of primary and hepatic lesions without neoadjuvant chemotherapy(NAC).We aim to investigate the prognosis of patients with resectable CRLM undergoing simultaneous resection of primary and hepatic lesions without NAC.Methods Data of patients with CRLM in the Surveillance,Epidemiology and End Results Program(cohort,n=225)were collected as the training set,and data of patients with CRLM treated at the National Cancer Center(cohort,n=180)were collected as the validation set.The prognostic value of the clinicopathological parameters in the training cohort was assessed using Kaplan‒Meier curves and univariate and multivariate Cox proportional hazards models,and OS and CSS nomograms integrated with the prognostic variables were constructed.Calibration analyses,receiver operating characteristic(ROC)curves,and decision curve analyses(DCAs)were then performed to evaluate the performance of the nomograms.Results There was no collinearity among the collected variables.Three factors were associated with OS and CSS:the pretreatment carcinoembryonic antigen(CEA)concentration,pathologic N(pN)stage,and adjuvant chemotherapy(each p<0.05).OS and CSS nomograms were constructed using these three parameters.The calibration plots revealed favorable agreement between the predicted and observed outcomes.The areas under the ROC curves were approximately 0.7.The DCA plots revealed that both nomograms had satisfactory clinical benefits.The ROC curves and DCAs also confirmed that the nomogram surpassed the tumor,node,and metastasis staging system.Conclusion The herein-described nomograms containing the pretreatment CEA concentration,pN stage,and adjuvant chemotherapy may be effective models for predicting postoperative survival in patients with CRLM.

Electrochemical aptasensor for the detection of vascular endothelial growth factor(VEGF) based on DNA-templated Ag/Pt bimetallic nanoclusters

In this paper, the DNA-templated Ag/Pt bimetallic nanoclusters were successfully synthesized using an optimized synthetic scheme. The obtained DNA-Ag/Pt NCs have an ultrasmall particle size and excellent distribution. The DNA-Ag/Pt NCs show intrinsic peroxidase-mimicking activity and can effectively catalyze the H2O2-mediated oxidation of a substrate, 3,30,5,50-tetramethylbenzidine（TMB）, to produce a blue colored product. Based on this specific property, we employed the aptamer of VEGF to design a label-free electrochemical biosensor for VEGF detection. Under the optimized experimental conditions, a linear range from 6.0 pmol/L to 20 pmol/L was obtained with a detection limit of 4.6 pmol/L. The proposed biosensor demonstrated its high specificity for VEGF and could directly detect the VEGF concentration in human serum samples of breast cancer patients with satisfactory results. This novel electrochemical aptasensor was simple and convenient to use and was cost-effective and label-free in design, and would hold potential applications in medical diagnosis and treatment.

Storage of osmotically treated entomopathogenic nematode Steinernema carpocapsae

The infective juveniles （IJs） ofSteinernema carpocapsae ‘All＇ were osmotically stressed by a mixture of ionic （fortified artificial seawater） and non-ionic （3.2 mol/L glycerol） solutions to establish a method for osmotic storage of entomopathogenic nematodes. Seven combinations （termed solution A to G） with different proportions of these two solutions were tested, with sterile extra pure water （sepH20, termed solution H） as a control. The mortality of the IJs at a concentration of 5×10^5 IJ/mL in the solutions A to G, and H were 13.2%, 16.2%, 16.7%, 13.5%, 25.2%, 31.6%, 44.6%, and 1.0%, respectively, after 21 days storage at 25℃. Most of the IJs shrunk and stopped motility after 6-9 hours incubation at 25℃ in solutions A to D. Based on the results, solutions A to D and H were chosen to further test the osmotic survival of the IJs at different IJ concentrations （5× 10^5, 2.5×10^5, 2 000 IJ/mL） and incubation temperature （30℃, 25℃, 10℃）. The resulting IJs were exposed to a high temperature assay （45℃ for 4 h, HTA）. Osmotically stressed IJs showed improved heat tolerance. The mortality of the Lls increased with the increasing concentrations of the test Lls and the storage temperatures after exposing to the HTA. More than 88.4%, 62.3% or 2.4% of the treated IJs died at the above three IJ concentrations, respectively. At the three IJ concentrations （2 000 IJs/mL, 2.5×10^5 IJs/mL or 5 ×10^5 IJs/mL）, the highest mortality was recorded in solution D （11.6%, 85.9% or 98.0%, respectively）, and the lowest mortality in solution B （2. 4%, 62.3% or 86.6%, respectively）. No untreated IJs survived after the heat treatment. During 42 days storage at 10℃, the IJs mortality in the solutiors A to D and H were 7.19%, 5.97%, 4.41%, 4.34%, and 4.34% respectively, and showed no significant differences. In conclusion, osmotic treatment of the IJs of S. carpocapsae ‘ All＇ in a mixture of ionic and non-ionic solutions enhances the heat tolerance. The mortality of the IJs after HTA increased with the increasing concentrations of the test IJs and the storage temperatures after exposure to the HTA. The result is promising for the osmotic storage of the entomopathogenic nematodes.

A unique photosystem I reaction center from a chlorophyll d-containing cyanobacterium Acaryochloris marina

Photosystem I(PSI)is a large protein supercomplex that catalyzes the light-dependent oxidation of plastocyanin(or cytochrome c6)and the reduction of ferredoxin.This catalytic reaction is realized by a transmembrane electron transfer chain consisting of primary electron donor(a special chlorophyll(Chl)pair)and electron acceptors A_(0),A_(1),and three Fe_(4)S_(4) clusters,F_(X),F_(A),and F_(B).Here we report the PSI structure from a Chl d-dominated cyanobacterium Acaryochloris marina at 3.3Åresolution obtained by single-particle cryo-electron microscopy.The A.marina PSI exists as a trimer with three identical monomers.Surprisingly,the structure reveals a unique composition of electron transfer chain in which the primary electron acceptor A_(0) is composed of two pheophytin a rather than Chl a found in any other well-known PSI structures.A novel subunit Psa27 is observed in the A.marina PSI structure.In addition,77 Chls,13α-carotenes,two phylloquinones,three Fe-S clusters,two phosphatidyl glycerols,and one monogalactosyl-diglyceride were identified in each PSI monomer.Our results provide a structural basis for deciphering the mechanism of photosynthesis in a PSI complex with Chl d as the dominating pigments and absorbing far-red light.