超高压处理对草鱼鱼肉风味物质的影响

以草鱼为原料,研究了不同超高压(0.1、100、200、300、400、500 MPa,保压10 min)条件处理后草鱼鱼肉的呈味核苷酸类物质、游离氨基酸以及挥发性物质的含量变化。结果表明:100、400和500 MPa压力处理后草鱼鱼肉的AMP含量显著增加(p0.05),200和300 MPa处理后则显著减少,100和300 MPa条件下IMP含量得到显著增加,而200、400和500 MPa条件下显著减少;不同压力条件对游离氨基酸的影响不一,100、300和400 MPa处理对草鱼鱼肉的游离氨基酸含量影响较小,而200和500 MPa压力则使得游离氨基酸总量显著减少;六组样品中分别检测到32、31、35、41、44和40种挥发性物质,其中以醛酮类和醇类为主,超高压处理后醇类的相对含量显著减少,醛酮类的相对含量则显著增加,并且200 MPa及以上的压力条件下醛酮类物质的种类也有所增加。     

不同生长阶段下中华绒螯蟹滋味成分差异研究

本文比较了8月份到12月份下中华绒螯蟹雄蟹滋味物质间的差异。通过用电子舌区分不同月份下中华绒螯蟹三个可食部位(体肉、性腺、肝胰腺)的滋味轮廓,并测定其游离氨基酸和呈味核苷酸含量,计算TAV值、EUC值,结果表明电子舌能较好区分不同月份下各可食部位滋味轮廓间的差异,11月份、12月份的滋味轮廓与8月份、9月份相比差异较大;三个可食部位中呈甜味氨基酸含量与性腺中呈鲜味氨基酸含量均在11月份达到最高;蟹肉中呈味核苷酸总量最高,且波动较大,11月份以后呈鲜味核苷酸和呈甜味核苷酸含量显著增高,而性腺和肝胰腺中呈味核苷酸含量波动较小;不同阶段下中华绒螯蟹各可食部位的Glu、Ala、Arg和Lys的TAV值均大于1,对蟹的整体滋味贡献较大;性腺中的EUC值显著高于其他部位,并且在9月份、12月份达到最高。综上,雄蟹在11月份滋味最佳。     

4-Pyridone-3-carboxamide-1-β-D-ribonucleoside (4PYR)—A Novel Oncometabolite Modulating Cancer-Endothelial Interactions in Breast Cancer Metastasis

The accumulation of specific metabolic intermediates is known to promote cancer progression. We analyzed the role of 4-pyridone-3-carboxamide-1-β-D-ribonucleoside (4PYR), a nucleotide metabolite that accumulates in the blood of cancer patients, using the 4T1 murine in vivo breast cancer model, and cultured cancer (4T1) and endothelial cells (ECs) for in vitro studies. In vivo studies demonstrated that 4PYR facilitated lung metastasis without affecting primary tumor growth. In vitro studies demonstrated that 4PYR affected extracellular adenine nucleotide metabolism and the intracellular energy status in ECs, shifting catabolite patterns toward the accumulation of extracellular inosine, and leading to the increased permeability of lung ECs. These changes prevailed over the direct effect of 4PYR on 4T1 cells that reduced their invasive potential through 4PYR-induced modulation of the CD73-adenosine axis. We conclude that 4PYR is an oncometabolite that affects later stages of the metastatic cascade by acting specifically through the regulation of EC permeability and metabolic controls of inflammation.     

Dry Polymerization of 3′,5′‐Cyclic GMP to Long Strands of RNA

Recent progress in the synthesis of nucleotides from prebiotically plausible precursors has opened up new ways to explain the origin of genetic matter. Mechanisms for the polymerization of nucleotides without the help of catalysts are, however, rare. Complementary to the experiments done by Costanzo et al., we found that drying 3′,5′‐cyclic GMP leads to poly‐G RNA strands with lengths of up to 40 nucleotides. We also show that the polymerization to long RNA strands is considerably more efficient under dry conditions than for cGMP polymerization in water. The length depends on the incubation time of dry nucleotides at temperatures of 40–80 °C. No enzymes or other catalysts are needed for successful polymerization.     

A multi-angular mass spectrometric view at cyclic nucleotide dependent protein kinases: in vivo characterization and structure/function relationships

Mass spectrometry has evolved in recent years to a well-accepted and increasingly important complementary technique in molecular and structural biology. Here we review the many contributions mass spectrometry based studies have made in recent years in our understanding of the important cyclic nucleotide activated protein kinase A (PKA) and protein kinase G (PKG). We both describe the characterization of kinase isozymes, substrate phosphorylation, binding partners and post-translational modifications by proteomics based methodologies as well as their structural and functional properties as revealed by native mass spectrometry, H/D exchange MS and ion mobility. Combining all these mass spectrometry based data with other biophysical and biochemical data has been of great help to unravel the intricate regulation of kinase function in the cell in all its magnificent complexity.     

DNA‐Binding Properties of New Fluorescent AzaHx Amides: Methoxypyridylazabenzimidazolepyrroleimidazole/pyrrole

DNA minor groove binding polyamides have been extensively developed to control abnormal gene expression. The establishment of novel, inherently fluorescent 2‐(p‐anisyl)benzimidazole (Hx) amides has provided an alternative path for studying DNA binding in cells by direct observation of cell localization. Because of the 2:1 antiparallel stacking homodimer binding mode of these molecules to DNA, modification of Hx amides to 2‐(p‐anisyl)‐4‐azabenzimidazole (AzaHx) amides has successfully extended the DNA‐recognition repertoire from central CG [recognized by Hx‐I (I=N‐methylimidazole)] to central GC [recognized by AzaHx‐P (P=N‐methylpyrrole)] recognition. For potential targeting of two consecutive GG bases, modification of the AzaHx moiety to 2‐ and 3‐pyridyl‐aza‐benzimidazole (Pyr‐AzaHx) moieties was explored. The newly designed molecules are also small‐sized, fluorescent amides with the Pyr‐AzaHx moiety connected to two conventional five‐membered heterocycles. Complementary biophysical methods were performed to investigate the DNA‐binding properties of these molecules. The results showed that neither 3‐Pyr‐AzaHx nor 2‐Pyr‐AzaHx was able to mimic I‐I=N‐methylimidazole–N‐methylimidazole to target GG dinucleotides specifically. Rather, 3‐Pyr‐AzaHx was found to function like AzaHx, f‐I (f=formamide), or P‐I as an antiparallel stacked dimer. 3‐Pyr‐AzaHx‐PI ( 2 ) binds 5′‐ACGCGT′‐3′ with improved binding affinity and high sequence specificity in comparison to its parent molecule AzaHx‐PI ( 1 ). However, 2‐Pyr‐AzaHx is detrimental to DNA binding because of an unfavorable steric clash upon stacking in the minor groove.