An Enzyme-Cleavable Solubilizing-Tag Facilitates the Chemical Synthesis of Mirror-Image Proteins

Mirror-image proteins (D-proteins) are useful in biomedical research for purposes such as mirror-image screening for D-peptide drug discovery, but the chemical synthesis of many D-proteins is often low yielding due to the poor solubility or aggregation of their constituent peptide segments. Here, we report a Lys-C protease-cleavable solubilizing tag and its use to synthesize difficult-to-obtain D-proteins. Our tag is easily installed onto multiple amino acids such as DLys, DSer, DThr, and/or the N-terminal amino acid of hydrophobic D-peptides, is impervious to various reaction conditions, such as peptide synthesis, ligation, desulfurization, and transition metal-mediated deprotection, and yet can be completely removed by Lys-C protease under denaturing conditions to give the desired D-protein. The efficacy and practicality of the new method were exemplified in the synthesis of two challenging D-proteins: D-enantiomers of programmed cell death protein 1 IgV domain and SARS-CoV-2 envelope protein, in high yield. This work demonstrates that the enzymatic cleavage of solubilizing tags under denaturing conditions is feasible, thus paving the way for the production of more D-proteins.

[A multicenter prospective study on early identification of refractory Mycoplasma pneumoniae pneumonia in children]

Objective: To explore potential predictors of refractory Mycoplasma pneumoniae pneumonia (RMPP) in early stage. Methods: The prospective multicenter study was conducted in Zhejiang, China from May 1st, 2019 to January 31st, 2020. A total of 1 428 patients with fever >48 hours to <120 hours were studied. Their clinical data and oral pharyngeal swab samples were collected; Mycoplasma pneumoniae DNA in pharyngeal swab specimens was detected. Patients with positive Mycoplasma pneumoniae DNA results underwent a series of tests, including chest X-ray, complete blood count, C-reactive protein, lactate dehydrogenase (LDH), and procalcitonin. According to the occurrence of RMPP, the patients were divided into two groups, RMPP group and general Mycoplasma pneumoniae pneumonia (GMPP) group. Measurement data between the 2 groups were compared using Mann-Whitney U test. Logistic regression analyses were used to examine the associations between clinical data and RMPP. Receiver operating characteristic (ROC) curves were used to analyse the power of the markers for predicting RMPP. Results: A total of 1 428 patients finished the study, with 801 boys and 627 girls, aged 4.3 (2.7, 6.3) years. Mycoplasma pneumoniae DNA was positive in 534 cases (37.4%), of whom 446 cases (83.5%) were diagnosed with Mycoplasma pneumoniae pneumonia, including 251 boys and 195 girls, aged 5.2 (3.3, 6.9) years. Macrolides-resistant variation was positive in 410 cases (91.9%). Fifty-five cases were with RMPP, 391 cases with GMPP. The peak body temperature before the first visit and LDH levels in RMPP patients were higher than that in GMPP patients (39.6 (39.1, 40.0) vs. 39.2 (38.9, 39.7) ℃, 333 (279, 392) vs. 311 (259, 359) U/L, both P<0.05). Logistic regression showed the prediction probability π=exp (-29.7+0.667×Peak body temperature (℃)+0.004×LDH (U/L))/(1+exp (-29.7+0.667×Peak body temperature (℃)+0.004 × LDH (U/L))), the cut-off value to predict RMPP was 0.12, with a consensus of probability forecast of 0.89, sensitivity of 0.89, and specificity of 0.67; and the area under ROC curve was 0.682 (95%CI 0.593-0.771, P<0.01). Conclusion: In MPP patients with fever over 48 to <120 hours, a prediction probability π of RMPP can be calculated based on the peak body temperature and LDH level before the first visit, which can facilitate early identification of RMPP.

L-Glycosidase-Cleavable Natural Glycans Facilitate the Chemical Synthesis of Correctly Folded Disulfide-Bonded D-Proteins

D-peptide ligands can be screened for therapeutic potency and enzymatic stability using synthetic mirror-image proteins (D-proteins), but efficient acquisition of these D-proteins can be hampered by the need to accomplish their in vitro folding, which often requires the formation of correctly linked disulfide bonds. Here, we report the finding that temporary installation of natural O-linked-β-N-acetyl-D-glucosamine (O-GlcNAc) groups onto selected D-serine or D-threonine residues of the synthetic disulfide-bonded D-proteins can facilitate their folding in vitro, and that the natural glycosyl groups can be completely removed from the folded D-proteins to afford the desired chirally inverted D-protein targets using naturally occurring O-GlcNAcase. This approach enabled the efficient chemical syntheses of several important but difficult-to-fold D-proteins incorporating disulfide bonds including the mirror-image tumor necrosis factor alpha (D-TNFα) homotrimer and the mirror-image receptor-binding domain of the Omicron spike protein (D-RBD). Our work establishes the use of O-GlcNAc to facilitate D-protein synthesis and folding and proves that D-proteins bearing O-GlcNAc can be good substrates for naturally occurring O-GlcNAcase.

Chemical synthesis of a 28 kDa full-length PET degrading enzyme ICCG by the removable backbone modification strategy

Chemical protein synthesis offers a powerful way to access otherwise-difficult-to-obtain proteins such as mirror-image proteins. Although a large number of proteins have been chemically synthesized to date, the acquisition to proteins containing hydrophobic peptide fragments has proven challenging. Here, we describe an approach that combines the removable backbone modification strategy and the peptide hydrazide-based native chemical ligation for the chemical synthesis of a 28 kDa full-length PET degrading enzyme IGGC (a higher depolymerization efficiency of variant leaf-branch compost cutinase (LCC)) containing hydrophobic peptide segments. The synthetic ICCG exhibits the enzymatic activity and will be useful in establishing the corresponding mirror-image version of ICCG.

Backbone-Installed Split Intein-Assisted Ligation for the Chemical Synthesis of Mirror-Image Proteins

Membrane-associated D-proteins are an important class of synthetic molecules needed for D-peptide drug discovery, but their chemical synthesis using canonical ligation methods such as native chemical ligation is often hampered by the poor solubility of their constituent peptide segments. Here, we describe a Backbone-Installed Split Intein-Assisted Ligation (BISIAL) method for the synthesis of these proteins, wherein the native L-forms of the N- and C-intein fragments of the unique consensus-fast (Cfa) (i.e. L-CfaN and L-CfaC ) are separately installed onto the two D-peptide segments to be ligated via a removable backbone modification. The ligation proceeds smoothly at micromolar (μM) concentrations under strongly chaotropic conditions (8.0 M urea), and the subsequent removal of the backbone modification groups affords the desired D-proteins without leaving any "ligation scar" on the products. The effectiveness and practicality of the BISIAL method are exemplified by the synthesis of the D-enantiomers of the extracellular domains of T cell immunoglobulin and ITIM domain (TIGIT) and tropomyosin receptor kinase C (TrkC). The BISIAL method further expands the chemical protein synthesis ligation toolkit and provides practical access to challenging D-protein targets.

Chemically Synthetic d-Sortase Enables Enzymatic Ligation of d-Peptides

We have described the chemical synthesis of d-Sortase A in large quantity and high purity by a hydrazide ligation strategy. The d-Sortase was fully active toward d-peptides and D/L hybrid proteins, and the ligation efficiency was unaffected by the chirality of the C-terminus substrate. This study points toward using d-sortase ligation as a modern ligation method for d-proteins and D/L hybrid proteins and expands the chemical protein synthesis toolbox in biotechnology.

Total Chemical Synthesis of Correctly Folded Disulfide-Rich Proteins Using a Removable O-Linked β-N-Acetylglucosamine Strategy

Disulfide-rich proteins are useful as drugs or tool molecules in biomedical studies, but their synthesis is complicated by the difficulties associated with their folding. Here, we describe a removable glycosylation modification (RGM) strategy that expedites the chemical synthesis of correctly folded proteins with multiple or even interchain disulfide bonds. Our strategy comprises the introduction of simple O-linked β-N-acetylglucosamine (O-GlcNAc) groups at the Ser/Thr sites that effectively improve the folding of disulfide-rich proteins by stabilization of their folding intermediates. After folding, the O-GlcNAc groups can be efficiently removed using O-GlcNAcase (OGA) to afford the correctly folded proteins. Using this strategy, we completed the synthesis of correctly folded hepcidin, an iron-regulating hormone bearing four pairs of disulfide-bonds, and the first total synthesis of correctly folded interleukin-5 (IL-5), a 26 kDa homodimer cytokine responsible for eosinophil growth and differentiation.

Removable Backbone Modification (RBM) Strategy for the Chemical Synthesis of Hydrophobic Peptides/Proteins

Chemical synthesis can provide hydrophobic proteins with natural or man-made modifications (e.g. S-palmitoylation, site-specific isotope labeling and mirror-image proteins) that are difficult to obtain through the recombinant expression technology. The difficulty of chemical synthesis of hydrophobic proteins stems from the hydrophobic nature. Removable backbone modificaiton (RBM) strategy has been developed for solubilizing the hydrophobic peptides/proteins. Here we take the chemical synthesis of a S-palmitoylated peptide as an example to describe the detailed procedure of RBM strategy. Three critical steps of this protocol are: (1) installation of Lys6-tagged RBM groups into the peptides by Fmoc (9-fluorenylmethyloxycarbonyl) solid-phase peptide synthesis, (2) chemical ligation of the peptides, and (3) removal of the RBM tags by TFA (trifluoroacetic acid) cocktails to give the target peptide.

Chemical Synthesis of a Full-Length G-Protein-Coupled Receptor β2-Adrenergic Receptor with Defined Modification Patterns at the C-Terminus

The β₂-adrenergic receptor (β₂AR) is a G-protein-coupled receptor (GPCR) that responds to the hormone adrenaline and is an important drug target in the context of respiratory diseases, including asthma. β₂AR function can be regulated by post-translational modifications such as phosphorylation and ubiquitination at the C-terminus, but access to the full-length β₂AR with well-defined and homogeneous modification patterns critical for biochemical and biophysical studies remains challenging. Here, we report a practical synthesis of differentially modified, full-length β₂AR based on a combined native chemical ligation (NCL) and sortase ligation strategy. An array of homogeneous samples of full-length β₂ARs with distinct modification patterns, including a full-length β₂AR bearing both monoubiquitination and octaphosphorylation modifications, were successfully prepared for the first time. Using these homogeneously modified full-length β₂AR receptors, we found that different phosphorylation patterns mediate different interactions with β-arrestin1 as reflected in different agonist binding affinities. Our experiments also indicated that ubiquitination can further modulate interactions between β₂AR and β-arrestin1. Access to full-length β₂AR with well-defined and homogeneous modification patterns at the C-terminus opens a door to further in-depth mechanistic studies into the structure and dynamics of β₂AR complexes with downstream transducer proteins, including G proteins, arrestins, and GPCR kinases.

[Study of the risk factors for recurrence of early and late stage hepatocellular carcinoma after hepatic artery embolization combined with radiofrequency ablation therapy]

Objective: To investigate the risk factors for recurrence of early and late stage hepatocellular carcinoma after receiving hepatic artery embolization combined with radiofrequency ablation therapy. Methods: 246 cases with hepatocellular carcinoma who underwent hepatic artery embolization combined with radiofrequency ablation in Beijing You'an Hospital Affiliated to Capital Medical University from January 2006 to January 2011 were selected. Clinical and follow-up data were collected. Univariate Cox analyses was used to determine the factors influencing recurrence of early and late stage HCC after hepatic artery embolization combined with radiofrequencies ablation. Multivariate Cox regression analysis was used to determine the independent factors. Results: 246 case with hepatocellular carcinoma were treated with hepatic artery embolization combined with radiofrequency ablation, with median follow-up time of 99 months. A total of 179 cases had recurrence and 67 cases had no recurrence. Considering 24 months as the limit, 95 cases had early recurrence and 84 cases had late recurrence. The 1-, 2-, 3-, 5-, and 10-year recurrence rates were 21.3%, 39.0%, 53.0%, 67.3%, and 77.6%, respectively. Multivariate Cox regression analysis showed that the maximum tumor diameter (HR = 2.183, 95% CI: 1.414-3.369, P < 0.01) and tumor number (HR = 1.681, 95% CI: 1.110-2.545, P < 0.05) were independent factor influencing recurrence of early stage HCC after hepatic artery embolization combined with radiofrequency ablation. Liver cirrhosis (HR = 0.421, 95% CI: 0.272-0.651, P < 0.01) was an independent factor influencing recurrence of late stage HCC after hepatic artery embolization combined with radiofrequency ablation. Conclusion: Tumor diameter and number are independent factors influencing recurrence of early stage HCC, while liver cirrhosis is an independent factor influencing recurrence of late stage HCC after hepatic artery embolization combined with radiofrequency ablation therapy.

[A prospective study of the effect and mechanism of autologous platelet-rich plasma combined with Meek microskin grafts in repairing the wounds of limbs in severely burned patients]

Objective: To observe the effect of autologous platelet-rich plasma (PRP) combined with Meek microskin grafts in repairing the wounds of limbs in severely burned patients, and to explore the mechanism. Methods: The prospective controlled research method was used. From September 2016 to January 2020, 16 patients aged 18-69 years, with extensive deep burns, including 9 males and 7 females, who met the selection criteria were admitted to the Department of Burns and Plastic Surgery of the 909th Hospital of the Joint Logistic Support Force of PLA. The bilateral limbs with similar injury in 8 patients were divided into Meek skin grafting+PRP group and Meek skin grafting alone group according to the random number table; in the other 8 patients, the limbs with severer injury were included in Meek skin grafting+PRP group, and the limbs on the other side were included in Meek skin grafting alone group. The wounds of affected limbs in the two groups were treated correspondingly. On post surgery day (PSD) 10, the survival and fusion of Meek microskin grafts were observed and the survival rate and fusion rate were calculated; the histological morphology and the angiogenesis of the basal tissue of Meek microskin graft were observed by hematoxylin-eosin staining and immunohistochemical staining, respectively, with the microvessels being counted. Data were statistically analyzed with paired sample t test. Results: On PSD 10, the wounds of affected limbs in Meek skin grafting+PRP group were dry, and most of the transplanted skin grafts were closely adhered to the basal tissue; while a small amount of exudate could be found in the wounds of affected limbs in Meek skin grafting alone group, and a small part of the transplanted microskin grafts fell off or poorly attached to the basal tissue. On PSD 10, the survival rate and the fusion rate of Meek microskin grafts in the wounds of affected limbs in Meek skin grafting+PRP group were (94±3)% and (86±4)%, which were significantly higher than (89±4)% and (79±4)% of Meek skin grafting alone group, respectively (t=3.633, 4.229, P<0.01). On PSD 10, the basal epidermis was closely connected with dermis of Meek microskin grafts in the wounds of affected limbs in Meek skin grafting+PRP group, with more inflammatory cell infiltration and active microvascular hyperplasia, while the basal epidermis was less closely connected with dermis of Meek microskin grafts in the wounds of affected limbs in Meek skin grafting alone group, with obvious degeneration of collagen fibers under the dermis, less inflammatory cell infiltration, and slightly poor microvascular hyperplasia. On PSD 10, the distribution of microvessels in basal tissue of Meek microskin grafts in the wounds of affected limbs in Meek skin grafting+PRP group were densely clustered, while the distribution of microvessels in Meek skin grafting alone group were scattered, sparse, and dotted. On PSD 10, the number of microvessels in basal tissue of Meek microskin grafts in the wounds of affected limbs in Meek skin grafting+PRP group was 36±6 in each 400-fold visual field, which was significantly more than 29±7 of Meek skin grafting alone group (t=2.671, P<0.05). Conclusions: Autologous PRP can effectively promote the survival rate and fusion rate of Meek microskin grafts in the wounds of limbs after escharectomy in severely burned patients by promoting angiogenesis at the base of Meek microskin grafts.

A mirror-image protein-based information barcoding and storage technology

A mirror-image protein-based information barcoding and storage technology wherein D-amino acids are used to encode information into mirror-image proteins that are chemically synthesized is described. These mirror-image proteins were then fused into various materials from which information-encoded objects were produced. Subsequently, the mirror-image proteins were extracted from the objects using biotin-streptavidin resin-mediated specific enrichment and cleaved using an Ni(II)-mediated selective peptide cleavage. Protein sequencing was accomplished using liquid chromatography/tandem mass spectrometry (LC-MS/MS) and then transcoded into the recorded information. We demonstrated the use of this technology to encode Chinese words into mirror-image proteins, which were then fused onto a poly(ethylene terephthalate) (PET) film and retrieved and decoded by LC-MS/MS sequencing. Compared to information barcoding and storage technologies using natural biopolymers, the mirror-image biopolymers used in our technology may be more stable and durable.

[Development and clinical application of custom-made temporomandibular joint-skull base combined prosthesis]

Objective: To introduce the design, manufacture and clinical application of the custom-made temporomandibular joint (TMJ)-skull base combined prosthesis and evaluate its safety, effectiveness and accuracy. Methods: The patients diagnosed with the TMJ-skull base lesion in Department of Oral Surgery, Shanghai Ninth People's Hospital from October 2016 to November 2020 were recruited in this study. The maxillofacial CT data for all the patients were obtained and transformed into the Mimics 18.0 software preoperatively. The custom-made TMJ-skull base combined prosthesis, included four components, was designed based on the anatomy, stress distribution and movement of the TMJ and skull base, and fabricated by three-dimensional printing and 5-axis milling technologies. The TMJ-skull base lesion was excised completely with the help of digital templates from modified preauricular and/or post and submandibular incisions. The combined prosthesis were implanted and fixed after the lesion resection. The examinations including general situation, cranio-maxillofacial structure and function were taken during and after surgery to assess its using effect. Results: Ten patients [6 females and 4 males, (43.2±13.6) years old] were included and all prostheses were positioned accurately and fixed excellently. After (29.4±17.3) months follow-up, the occlusion relationship was stable and no adverse symptoms such as dizziness, headache, meningeal irritation and permanent facial nerve injury occurred. The pain, diet, mandibular movement function, lateral movement to diseased side and mouth opening had significant improvements. The forward movement and lateral movement to normal side were not improved significantly. There were no prosthesis displacement, loosening and fracture in X-ray and CT postoperatively. With the pre and postoperative craniomaxillofacial model merging, the maximal implanted error was (0.52±0.17) mm for fossa and condyle and (1.62±0.26) mm for skull base and mandibular handle in surface deviation analysis. Conclusions: The custom-made TMJ-skull base combined prosthesis with customized design and 3D printing fabrication is safe, effective and precise in clinical application.

[Lee T'ao: the pioneer of educator and researcher of Chinese medical history]

Lee T'ao(1901-1959),studied at Beijing National Medical Institute in 1921.He worked at the Chinese Department of Concord Medical Institute from 1928-1942. He studied medical history and taught the history of western and Chinese medicines. He finished Medical History Profile in 1940.During this period, he and Concord Medical Institute collaborated to collect Chinese medical books, therefore he became one of Chinese Medical Association. After 1946, he worked at Medical School of Beijing University (later change its name into Beijing Medical Institute), and he was professor, lead of Medical Teaching and Research Office. He also joined the Editorial department of the Chinese Journal of Medical History, and edited the list of western and Chinese medical books. He published many papers of the Chinese medical history, which had broad vision and novel viewpoint. For the teaching and research, he focused on fieldwork, and physical cultural and historical relics. He investigated and surveyed some high valuable historical relics of medicine that belonged to many of Chinese dynasties. In 1954, he also worked as a lead at the office of medical history for Chinese Central Research Institute. In 1956, he collaborated with Chen Bangxian, teaching the advanced classes for the teachers. He trained many medical history researchers and teachers.

Sarcolipin alters SERCA1a interdomain communication by impairing binding of both calcium and ATP

Sarcolipin (SLN), a single-spanning membrane protein, is a regulator of the sarco-endoplasmic reticulum Ca2+-ATPase (SERCA1a). Chemically synthesized SLN, palmitoylated or not (pSLN or SLN), and recombinant wild-type rabbit SERCA1a expressed in S. cerevisiae design experimental conditions that provide a deeper understanding of the functional role of SLN on the regulation of SERCA1a. Our data show that chemically synthesized SLN interacts with recombinant SERCA1a, with calcium-deprived E2 state as well as with calcium-bound E1 state. This interaction hampers the binding of calcium in agreement with published data. Unexpectedly, SLN has also an allosteric effect on SERCA1a transport activity by impairing the binding of ATP. Our results reveal that SLN significantly slows down the E2 to Ca2.E1 transition of SERCA1a while it affects neither phosphorylation nor dephosphorylation. Comparison with chemically synthesized SLN deprived of acylation demonstrates that palmitoylation is not necessary for either inhibition or association with SERCA1a. However, it has a small but statistically significant effect on SERCA1a phosphorylation when various ratios of SLN-SERCA1a or pSLN-SERCA1a are tested.

A genetically encoded small-size fluorescent pair reveals allosteric conformational changes of G proteins upon its interaction with GPCRs by fluorescence lifetime based FRET

The dynamics of GPCRs (G protein-coupled receptors) coupling for cognate G proteins play a critical role in signal transduction. Herein, we reported a site-specifically labelled small-sized fluorescent pair 7-HC/FlAsH ((7-hydroxycoumarin-4-yl)-ethylglycine/fluorescein arsenical hairpin) for fluorescence lifetime based FRET (fluorescence resonance energy transfer) to reveal conformational differences of Gαi1 (inhibitory G proteins) and Gαs (stimulatory G proteins) upon β2AR (β2-adrenergic receptor) coupling. It offers a new generally applicable method to probe protein dynamic interactions or conformational changes.

Synthesis of Disulfide Surrogate Peptides Incorporating Large-Span Surrogate Bridges Through a Native-Chemical-Ligation-Assisted Diaminodiacid Strategy

The use of synthetic bridges as surrogates for disulfide bonds has emerged as a practical strategy to obviate the poor stability of some disulfide-containing peptides. However, peptides incorporating large-span synthetic bridges are still beyond the reach of existing methods. Herein, we report a native chemical ligation (NCL)-assisted diaminodiacid (DADA) strategy that enables the robust generation of disulfide surrogate peptides incorporating surrogate bridges up to 50 amino acids in length. This strategy provides access to some highly desirable but otherwise impossible-to-obtain disulfide surrogates of bioactive peptide. The bioactivities and structures of the synthetic disulfide surrogates were verified by voltage clamp assays, NMR, and X-ray crystallography; and stability studies established that the disulfide replacements effectively overcame the problems of disulfide reduction and scrambling that often plague these pharmacologically important peptides.

Thiirane linkers directed histone H2A diubiquitination suggests plasticity in 53BP1 recognition

Polyubiquitination with diverse linkages on histones provides another layer of accuracy and complexity for epigenetic regulation, which is rarely studied. Herein, K27 or K48-diubiquitin modified H2A analogues were chemically synthesized using thiirane linkers. These permitted in vitro binding studies suggested the plasticity of ubiquitin chains in 53BP1 recognition.

Ligation of Soluble but Unreactive Peptide Segments in the Chemical Synthesis of Haemophilus Influenzae DNA Ligase

During the total chemical synthesis of the water-soluble globular Haemophilus Influenzae DNA ligase (Hin-Lig), we observed the surprising phenomenon of a soluble peptide segment that failed to undergo native chemical ligation. Based on dynamic light scattering and transmission electron microscopy experiments, we determined that the peptide formed soluble colloidal particles in a homogeneous solution containing 6 m guanidine hydrochloride. Conventional peptide performance-improving strategies, such as installation of a terminal/side-chain Arg tag or O-acyl isopeptide, failed to enable the reaction, presumably because of their inability to disrupt the formation of soluble colloidal particles. However, a removable backbone modification strategy recently developed for the synthesis of membrane proteins did disrupt the formation of the colloids, and the desired ligation of this soluble but unreactive system was eventually accomplished. This work demonstrates that an appropriate solution dispersion state, in addition to good peptide solubility, is a prerequisite for successful peptide ligation.

[Study on themisprints of the primary version of the Compendium of Materia Medica]

The Jinling version of the Compendium of Materia Medica was the primary version.It accurately represented the ideas of LI Shizhen, therefore it was valued by the scholars.There were many defects in misprint (knife carving) and proofreading.The main errors were some Chinese character's strokes missing and wrong characters printed.The authors collected some statistics data andmade some statistical analysis. They found that total misprints were 376 and emerge 615 times.Those misprints can divide into two categories: lack of some parts of Chinese characters; lack of some strokes of Chinese characters.Four tables which list the misprints was made.It is helpful for scholars to examine Compendium of Materia Medica or the study of other similar ancient literatures.

One-pot multi-segment condensation strategies for chemical protein synthesis

This paper describes recent advances of one-pot multi-segment condensation strategies based on kinetically controlled strategies and/or protecting group-removal strategies in chemical protein synthesis.

Select antibiotics in leachate from closed and active landfills exceed thresholds for antibiotic resistance development

Though antibiotic resistance (ABR) represents a major global health threat, contributions of landfill leachate to the life cycle of antibiotics and ABR development are poorly understood in rapidly urbanizing regions of developing countries. We selected one of the largest active landfills in Asia and two landfills that have been closed for 20 years to examine antibiotic occurrences in leachates and associated hazards during wet and dry season sampling events. We focused on some of the most commonly used human antibiotics in Hong Kong, one of the most populous Asian cities and the fourth most densely populated cities in the world. Seven antibiotics (cephalexin [CLX], chloramphenicol [CAP], ciprofloxacin [CIP], erythromycin [ERY], roxithromycin [ROX], trimethoprim [TMP], sulfamethoxazole [SMX]) were quantitated using HPLC-MS/MS generally following previously reported methods. Whereas CLX, CAP, ROX and SMX in leachates did not exceed ABR predicted no effect concentrations (PNECs), exceedances were observed for CIP, ERY and TMP in some study locations and on some dates. In fact, an ABR PNEC for CIP was exceeded in leachates during both sampling periods from all study locations, including leachates that are directly discharged to coastal systems. These findings highlight the importance of developing an advanced understanding of pharmaceutical access, usage and disposal practices, effectiveness of intervention strategies (e.g., leachate treatment technologies, drug take-back schemes), and contributions of landfill leachates to the life cycle of antibiotics and ABR development, particularly in rapidly urbanizing coastal regions with less advanced waste management systems than Hong Kong.

PI(4,5)P2 determines the threshold of mechanical force-induced B cell activation

B lymphocytes use B cell receptors (BCRs) to sense the chemical and physical features of antigens. The activation of isotype-switched IgG-BCR by mechanical force exhibits a distinct sensitivity and threshold in comparison with IgM-BCR. However, molecular mechanisms governing these differences remain to be identified. In this study, we report that the low threshold of IgG-BCR activation by mechanical force is highly dependent on tethering of the cytoplasmic tail of the IgG-BCR heavy chain (IgG-tail) to the plasma membrane. Mechanistically, we show that the positively charged residues in the IgG-tail play a crucial role by highly enriching phosphatidylinositol (4,5)-biphosphate (PI(4,5)P2) into the membrane microdomains of IgG-BCRs. Indeed, manipulating the amounts of PI(4,5)P2 within IgG-BCR membrane microdomains significantly altered the threshold and sensitivity of IgG-BCR activation. Our results reveal a lipid-dependent mechanism for determining the threshold of IgG-BCR activation by mechanical force.

Hmb(off/on) as a switchable thiol protecting group for native chemical ligation

A new thiol protecting group Hmb(off/on) is described, which has a switchable activity that may be useful in the chemical synthesis of proteins. When placed on the side chain of Cys, Cys(Hmb(off)) is stable to trifluoroacetic acid (TFA) in the process of solid-phase peptide synthesis. When Cys(Hmb(off)) is treated with neutral aqueous buffers, it is cleanly converted to acid-labile Cys(Hmb(on)), which can later be fully deprotected by TFA to generate free Cys. The utility of Cys(Hmb(off/on)) is demonstrated by the chemical synthesis of an erythropoietin segment, EPO[Cys(98)-Arg(166)]-OH through native chemical ligation.

Chemically synthesized histone H2A Lys13 di-ubiquitination promotes binding of 53BP1 to nucleosomes

This corrects the article DOI: 10.1038/cr.2017.157.

Convergent Total Synthesis of Histone H2B Protein with Site-Specific Ubiquitination at Lys120

Histone H2B Lys120 mono-ubiquitylation (H2BK120Ub) plays an important role in regulating gene expression and diverse nuclear processes. For biochemical and biophysical studies of this dynamic post-translational modification, access to homogeneous and workable amount of H2BK120Ub is obligatory. Here we report a new strategy for the convergent total chemical synthesis of homogenous histone H2BK120Ub on multi-milligram scale through the combination of hydrazide-based native chemical ligation and acid-cleavable auxiliary-mediated ligation of peptide hydrazides. The synthetic H2BK120Ub could be efficiently incorporated into nucleosomes, which may provide valuable materials for the biochemical and structural studies of nucleosome complexes involving H2BK120Ub.

Removable Backbone Modification Method for the Chemical Synthesis of Membrane Proteins

Chemical synthesis can produce water-soluble globular proteins bearing specifically designed modifications. These synthetic molecules have been used to study the biological functions of proteins and to improve the pharmacological properties of protein drugs. However, the above advances notwithstanding, membrane proteins (MPs), which comprise 20-30% of all proteins in the proteomes of most eukaryotic cells, remain elusive with regard to chemical synthesis. This difficulty stems from the strong hydrophobic character of MPs, which can cause considerable handling issues during ligation, purification, and characterization steps. Considerable efforts have been made to improve the solubility of transmembrane peptides for chemical ligation. These methods can be classified into two main categories: the manipulation of external factors and chemical modification of the peptide. This Account summarizes our research advances in the development of chemical modification especially the two generations of removable backbone modification (RBM) strategy for the chemical synthesis of MPs. In the first RBM generation, we install a removable modification group at the backbone amide of Gly within the transmembrane peptides. In the second RBM generation, the RBM group can be installed into all primary amino acid residues. The second RBM strategy combines the activated intramolecular O-to-N acyl transfer reaction, in which a phenyl group remains unprotected during the coupling process, which can play a catalytic role to generate the activated phenyl ester to assist in the formation of amide. The key feature of the RBM group is its switchable stability in trifluoroacetic acid. The stability of these backbone amide N-modifications toward TFA can be modified by regulating the electronic effects of phenol groups. The free phenol group is acylated to survive the TFA deprotection step, while the acyl phenyl ester will be quantitatively hydrolyzed in a neutral aqueous solution, and the free phenol group increases the electron density of the benzene ring to make the RBM labile to TFA. The transmembrane peptide segment bearing RBM groups behaves like a water-soluble peptide during fluorenylmethyloxycarbonyl based solid-phase peptide synthesis (Fmoc SPPS), ligation, purification, and characterization. The quantitative removal of the RBM group can be performed to obtain full-length MPs. The RBM strategy was used to prepare the core transmembrane domain Kir5.1[64-179] not readily accessible by recombinant protein expression, the influenza A virus M2 proton channel with phosphorylation, the cation-specific ion channel p7 from the hepatitis C virus with site-specific NMR isotope labels, and so on. The RBM method enables the practical engineering of small- to medium-sized MPs or membrane protein domains to address fundamental questions in the biochemical, biophysical, and pharmaceutical sciences.

Chemical Synthesis of K34-Ubiquitylated H2B for Nucleosome Reconstitution and Single-Particle Cryo-Electron Microscopy Structural Analysis

Post-translational modifications (e.g., ubiquitylation) of histones play important roles in dynamic regulation of chromatin. Histone ubiquitylation has been speculated to directly influence the structure and dynamics of nucleosomes. However, structural information for ubiquitylated nucleosomes is still lacking. Here we report an alternative strategy for total chemical synthesis of homogenous histone H2B-K34-ubiquitylation (H2B-K34Ub) by using acid-cleavable auxiliary-mediated ligation of peptide hydrazides for site-specific ubiquitylation. Synthetic H2B-K34Ub was efficiently incorporated into nucleosomes and further used for single-particle cryo-electron microscopy (cryo-EM) imaging. The cryo-EM structure of the nucleosome containing H2B-K34Ub suggests that two flexible ubiquitin domains protrude between the DNA chains of the nucleosomes. The DNA chains around the H2B-K34 sites shift and provide more space for ubiquitin to protrude. These analyses indicated local and slight structural influences on the nucleosome with ubiquitylation at the H2B-K34 site.

Apocynin Attenuates Cerebral Infarction after Transient Focal Ischaemia in Rats

This study investigated whether inhibition of reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase attenuates cerebral infarction after transient focal ischaemia in rats. Focal ischaemia (1.5 h) was produced in male Sprague-Dawley rats (250 − 280 g) by middle cerebral artery occlusion. Some rats also received treatment with 50 mg/kg apocynin, a NADPH oxidase inhibitor, by intraperitoneal injection 30 min prior to reperfusion. Two hours after reperfusion, brains were harvested to measure NADPH oxidase activity and superoxide levels. After 24 h, the remaining brains were harvested to investigate infarct size. NADPH oxidase activity and superoxide level were all augmented 2 h after reperfusion compared with controls. Apocynin treatment significantly reduced NADPH oxidase activity and superoxide levels. Cerebral infarct size was significantly smaller in the apocynin-treated group compared with those undergoing ischaemia/reperfusion alone. These results indicate that inhibition of NADPH oxidase attenuates cerebral infarction after transient focal ischaemia in rats, suggesting that inhibition of NADPH oxidase may provide a therapeutic strategy for ischaemic stroke.

Total chemical synthesis of the site-selective azide-labeled [I66A]HIV-1 protease

The first total chemical synthesis of the site-selective azide-labeled [I66A]HIV-1 protease is described by native chemical ligation. Chemical synthesis of azide-labeled proteins would provide useful protein tools for biochemical, biophysical or medical studies.

Total synthesis of mambalgin-1/2/3 by two-segment hydrazide-based native chemical ligation

Mambalgins are a class of 57-residue polypeptide toxins isolated from the venom of the African mamba. They exhibit potent analgesic effects by inhibiting the acid-sensing ion channels. Classified as members of the family of three-finger toxins, mambalgins contain four pairs of disulfide bridges that help to stabilize the three-finger scaffold. Here, we report the chemical synthesis of functional mambalgin-1/2/3 by using one-step two-segment hydrazide-based native chemical ligation. The two-segment ligation approach reported here may enable efficient production of mambalgin toxins. These synthetic mambalgins are useful compounds for development of diagnostic or therapeutic reagents. Copyright © 2016 European Peptide Society and John Wiley & Sons, Ltd.

Robust Chemical Synthesis of Membrane Proteins through a General Method of Removable Backbone Modification

Chemical protein synthesis can provide access to proteins with post-translational modifications or site-specific labelings. Although this technology is finding increasing applications in the studies of water-soluble globular proteins, chemical synthesis of membrane proteins remains elusive. In this report, a general and robust removable backbone modification (RBM) method is developed for the chemical synthesis of membrane proteins. This method uses an activated O-to-N acyl transfer auxiliary to install in the Fmoc solid-phase peptide synthesis process a RBM group with switchable reactivity toward trifluoroacetic acid. The method can be applied to versatile membrane proteins because the RBM group can be placed at any primary amino acid. With RBM, the membrane proteins and their segments behave almost as if they were water-soluble peptides and can be easily handled in the process of ligation, purification, and mass characterizations. After the full-length protein is assembled, the RBM group can be readily removed by trifluoroacetic acid. The efficiency and usefulness of the new method has been demonstrated by the successful synthesis of a two-transmembrane-domain protein (HCV p7 ion channel) with site-specific isotopic labeling and a four-transmembrane-domain protein (multidrug resistance transporter EmrE). This method enables practical synthesis of small- to medium-sized membrane proteins or membrane protein domains for biochemical and biophysical studies.

Total chemical synthesis of photoactivatable proteins for light-controlled manipulation of antigen-antibody interactions

We report the chemical synthesis of the first photo-activatable protein antigen that can be used to study antigen-antibody interaction mediated responses in B cells. This strategy facilitated fine tuning of the caged protein antigen to optimize its bioactivity and photochemical properties. One optimal molecule, HEL-K96NPE, was totally inert to hen egg lysozyme (HEL)-specific B cells and could only restore its antigenicity upon photoactivation. Combined with real time live cell imaging, the utility of HEL-K96NPE was demonstrated as a proof of concept to quantify B cell synapse formation and calcium influx responses at the single cell level.

[Efficacy evaluation and exploration of TACE combined with CT-guided precision microwave ablation treatment for primary liver cancer]

OBJECTIVE

To analyze the clinical therapeutic efficacy of transcatheter arterial chemoembolization combined with CT-guided percutaneous precision microwave ablation for the treatment of primary liver cancer and its influencing factors.

METHODS

A total of 126 patients with primary liver cancer were treated by transcatheter arterial chemoembolization combined with CT-guided percutaneous precision microwave ablation from Mar 2010 to Oct 2014 in our center. The treatment effect, postoperative complications and recurrence rates were observed, and the factors related to recurrence and survival time were analyzed.

RESULTS

All 126 primary liver cancer patients with 201 tumors were ablated for 177 times, and 113 cases with 185 tumors were completed ablated, the complete ablation rate was 92.0%. In all patients, 4 cases had serious complications, the incidence rate was 3.2%. 37 cases had recurrence, with a recurrence rate of 29.4%. All patients were followed up for 10 to 65 months, 17 patients died, and the 1-, 2-, and 3-year cumulative survival rates were 95.2%, 88.1%, and 84.1%, respectively, and the 1-, 2-, and 3-year progression-free-survival rates were 81.5%, 62.7% and 49.2%, respectively .Univariate analysis showed that preoperative AFP level, Child-Pugh score, BCLC stage and the largest tumor size were associated with the survival of patients who received TACE combined with CT-guided precision MWA, and the preoperative AFP level, internal medicine therapy, tumor number and the largest tumor size were associated with the progression-free-survival after the treatment (P<0.05). Multivariate analysis showed that Child-Pugh score and BCLC stage were independent factors affecting the survival of patients with primary liver cancer patients treated with TACE combined with CT guided percutaneous MWA, and the tumor number and the maximum tumor size were independent factors affecting the progression-free-survival of the patients (P<0.05).

CONCLUSION

TACE combined with CT-guided percutaneous precision microwave ablation therapy for primary liver cancer has reliable safety and efficacy.

Efficient synthesis of longer Aβ peptides via removable backbone modification

This paper describes a new method for the efficient chemical synthesis of longer Aβ peptides with the combination of the RBM strategy and native chemical ligation.

Protein/peptide secondary structural mimics: design, characterization, and modulation of protein–protein interactions

This review discusses general aspects of novel artificial peptide secondary structure mimics for modulation of PPIs, their therapeutic applications and future prospects.