In-vitro study on calcium carbonate crystal growth mediated by organic matrix extracted from fresh water pearls

The N-terminal polypeptide of a new shell matrix protein hicraqin accelerates the rate of calcium carbonate deposition

Matrix proteins play important roles in shell formation by regulating the assembly of organic matrix and minerals. Here, we obtained a new matrix protein (hicraqin) from Hyriopsis cumingii. The amino acid sequence of hicraqin contains multiple aggregated (Gly)n (n > 2) residues, a feature unique to silk-like matrix proteins. In situ hybridization studies and tissue expression patterns demonstrated that hicraqin may be a prismatic layer matrix protein. In vitro experiments were performed using the peptide N-hicraqin (the N-terminal free sequence of hicraqin). In the in vitro crystallization of calcium carbonate, crystals resembling dumbbell, spindle, and lotus aragonite crystals were observed under scanning electron microscopy and confirmed as calcite by Raman spectroscopy. In the in vitro crystallization system of calcium carbonate with the addition of magnesium ions, aragonite plates were generated with 50 μg/mL of the peptide N-hicraqin. The fluorescent labeling analysis indicated that N-hicraqin was involved in the crystallization process. The crystallization rate experiment showed that the peptide N-hicraqin plays a role in promoting crystallization. Following the silencing of the hicraqin gene by RNA interference, its expression was reduced by about 61 %. There was incomplete formation of the organic framework outside the prismatic layer. Overall, the present study showed that N-hicraqin participates in the crystallization process and acts as a framework protein that influences the formation of the organic framework of the prismatic layer.

Utilizing X-ray diffraction in conjunction with competitive adaptive reweighted sampling (CARS) and principal component analysis for the discrimination of medicinal pearl powder and nacre powder

Nacre powder, often utilized to counterfeit medicinal pearl powder due to their similar chemical composition and appearance, poses a challenge in product authentication. This study introduces a rapid and efficient method for distinguishing between medicinal pearl powder and nacre powder using X-ray diffraction in conjunction with principal component analysis (PCA). The X-ray diffraction pattern underwent preprocessing techniques including smoothing denoising (Savitzky-Golay filter, 5-point) and second-order derivative analysis. Subsequently, PCA was employed for dimensionality reduction modeling. The CARS method was applied to select optimal variables for model refinement, determining the data preprocessing approach and key modeling variables. This method demonstrates the capability to accurately differentiate between pearl powder, nacre powder, and even counterfeit samples containing up to 90% pearl powder. With a high accuracy rate, swift operational speed, and potential for automation, this approach shows promise for practical implementation in the realm of pearl powder quality control.

A Novel Kunitz-Type Serine Protease Inhibitor (HcKuSPI) is Involved in Antibacterial Defense in Innate Immunity and Participates in Shell Formation of Hyriopsis cumingii

Serine protease inhibitors (SPIs) are abundantly reported for its inhibition against specific proteases involved in the immune responses, but SPI data related to calcareous shells are scarce. Previously, our research group has reported the proteome analysis of non-nucleated pearl powder, and a candidate matrix protein containing two Kunitz domains in the acid soluble fraction caught our attention. In the present study, the full-length cDNA sequence of HcKuSPI was obtained from Hyriopsis cumingii. HcKuSPI was specifically expressed in the mantle, with hybridization signals mainly concentrated to dorsal epithelial cells at the mantle edge and weak signals at the mantle pallium, suggesting HcKuSPI was involved in shell formation. HcKuSPI expression in the mantle was upregulated after Aeromonas hydrophila and Staphylococcus aureus challenge to extrapallial fluids (EPFs). A glutathione S transferase (GST)-HcKuSPI recombinant protein showed strong inhibitory activity against the proteases, trypsin and chymotrypsin. Moreover, HcKuSPI expression in an experimental group was significantly higher when compared with a control group during pellicle growth and crystal deposition in shell regeneration processes, while the organic shell framework of newborn prisms and nacre tablets was completely destroyed after HcKuSPI RNA interference (RNAi). Therefore, HcKuSPI secreted by the mantle may effectively neutralize excess proteases and bacterial proteases in the EPF during bacterial infection and could prevent matrix protein extracellular degradation by suppressing protease proteolytic activity, thereby ensuring a smooth shell biomineralization. In addition, GST-HcKuSPI was also crucial for crystal morphology regulation. These results have important implications for our understanding of the potential roles of SPIs during shell biomineralization.

The Application of Pearls in Traditional Medicine of China and Their Chemical Constituents, Pharmacology, Toxicology, and Clinical Research

Although pearls are well known by most people, their medicinal value has not been popularized. This article collates the medicinal history of pearls over 2,000 years in China, including the application of pearls in the traditional medicine of China and their various preparations, as well as the progress of their chemical constituents, pharmacology, toxicology, and clinical research. Pearls from three different sources are used as medical materiel by 9 nationalities and 251 prescription preparations in China. In addition, pearls contain various inorganic constituents, such as calcium carbonate, trace elements, and water, and organic constituents, such as amino acids. In terms of pharmacology, pearls have many effects such as calming, improving cognitive ability, being anti-epileptic, promoting bone growth and regeneration, promoting the proliferation and migration of human microvascular endothelial cells, protecting the heart, anti-hemolysis, and anti-oxidation. In terms of toxicology, pearls are safe to take for a long time without exerting obvious adverse reactions. In terms of clinical application, pearls have been used to treat many diseases and conditions, such as convulsions, epilepsy, palpitations, eye diseases, ulcer diseases, skin diseases, or skin lesions. This article provides a reference for the application and research of pearls in the future.

Hic12, a novel acidic matrix protein promotes the transformation of calcite into vaterite in Hyriopsis cumingii

Shell acidic matrix proteins are widely considered to be essential for shell formation given their low affinity and high loading for calcium ion. In the present study, a novel matrix protein, hic12, was isolated from the mantle of Hyriopsis cumingii. High expression in tissue and positive signals with in situ hybridization were detected in the mantle center and mantle pallium, indicating that hic12 mainly participated in the biomineralization of the shell nacreous layer. The expression pattern of hic12 in the pearl sac during early pearl formation indicated that it was involved in pearl biomineralization. Moreover, the recombinant protein, rGST-Hic12, was successfully expressed and purified. The addition of rGST-Hic12 could accelerate the calcium carbonate deposition rate, change the morphology of crystals, and promote the conversion of calcite to vaterite. These results may provide new insights into the molecular mechanisms of aragonite mollusk shell formation.

In vitro crystallization of calcium carbonate mediated by proteins extracted from P. placenta shells

The ASM extracted from the shells of P. placenta can stabilize ACC and inhibit secondary nucleation for 10 hours, and an explosive secondary nucleation and quick crystal growth from 50 nm to 10 μm can be finished on the shell surface in one hour.

Therapeutic Effect of Seawater Pearl Powder on UV-Induced Photoaging in Mouse Skin

The objective of this study was to investigate the therapeutic effect of seawater pearl powder (SPP) on ultraviolet (UV) irradiation-induced photoaging in mouse skin. The protein and trace elements in SPP were detected by liquid chromatography-mass spectrometry, atomic fluorescence spectrometry, and inductively coupled plasma-atomic emission spectrometry. The effect of SPP on treating skin damage resulting from UV-induced photoaging was observed by gross physical appearance and histopathological analysis. Oxidative stress and melanin synthesis were analyzed using biochemical method. Western blotting was applied to analyze the phosphorylation and expression levels of matrix metalloproteinase-1 (MMP-1), collagen I, and proteins involved in the mitogen-activated protein kinase (MAPK) signaling pathways (p38, ERK, and JNK). The results show that SPP has a significant therapeutic effect on UV-induced photoaging of skin and improves and restores appearance and tissue structure of mouse skin. The major mechanism may be related to reduction of expression level of MMP-1 and enhancement of collagen I production via inhibition of MAPK signaling pathway after scavenging of excess reactive oxygen species (ROS) in the UV-induced photoaged skin of mice. Meanwhile, it may also be involved in reducing melanin content by inhibiting tyrosinase activity after scavenging excess ROS in the UV-induced photoaged skin of mice. Therefore, SPP could be a good substance to treat photoaging skin. Taking cost-effectiveness and efficacy into consideration, the optimal concentration of SPP for treating photoaging skin could be 100 mg/g.

Teosin, a novel basic shell matrix protein from Hyriopsis cumingii induces calcium carbonate polycrystal formation

In this study, a novel matrix protein (teosin) was isolated from Hyriopsis cumingii. Gene expression analysis showed that teosin is mainly expressed in the mantle and blood, and a hybridization signal was found in dorsal epithelial cells of the mantle pallial by in situ hybridization. Moreover, teosin expression during pearl formation indicated its participation in initial nacreous layer biomineralization, and suppressing teosin expression resulted in irregular crystal morphology and disordered arrangement in RNAi assay. In vitro crystallization assays indicated teosin could increase the size of calcite. By turning the sample stage about 15°, we got the high-resolution TEM images of the crystals' edges. This is a novel method to observe the crystal which is over 200 nm under TEM. In the control experiment group, the calcite show the character of long range order. The calcite induced by teosin were composed of nano-grains, and the polycrystal character were confirmed by EDS. These results suggested that teosin is involved in regulating crystal morphology regulation and inducing polycrystal formation during nacreous-layer formation.

Rapid identification of pearl powder from Hyriopsis cumingii by Tri-step infrared spectroscopy combined with computer vision technology

Pearl powder, an important raw material in cosmetics and Chinese patent medicines, is commonly uneven in quality and frequently adulterated with low-cost shell powder in the market. The aim of this study is to establish an adequate approach based on Tri-step infrared spectroscopy with enhancing resolution combined with chemometrics for qualitative identification of pearl powder originated from three different quality grades of pearls and quantitative prediction of the proportions of shell powder adulterated in pearl powder. Additionally, computer vision technology (E-eyes) can investigate the color difference among different pearl powders and make it traceable to the pearl quality trait-visual color categories. Though the different grades of pearl powder or adulterated pearl powder have almost identical IR spectra, SD-IR peak intensity at about 861cm^-1 (v₂ band) exhibited regular enhancement with the increasing quality grade of pearls, while the 1082cm^-1 (v₁ band), 712cm^-1 and 699cm^-1 (v₄ band) were just the reverse. Contrastly, only the peak intensity at 862cm^-1 was enhanced regularly with the increasing concentration of shell powder. Thus, the bands in the ranges of (1550-1350cm^-1, 730-680cm^-1) and (830-880cm^-1, 690-725cm^-1) could be exclusive ranges to discriminate three distinct pearl powders and identify adulteration, respectively. For massive sample analysis, a qualitative classification model and a quantitative prediction model based on IR spectra was established successfully by principal component analysis (PCA) and partial least squares (PLS), respectively. The developed method demonstrated great potential for pearl powder quality control and authenticity identification in a direct, holistic manner.

A Novel Matrix Protein Hic31 from the Prismatic Layer of Hyriopsis Cumingii Displays a Collagen-Like Structure

In this study, we clone and characterize a novel matrix protein, hic31, from the mantle of Hyriopsis cumingii. The amino acid composition of hic31 consists of a high proportion of Glycine residues (26.67%). Tissue expression detection by RT-PCR indicates that hic31 is expressed specifically at the mantle edge. In situ hybridization results reveals strong signals from the dorsal epithelial cells of the outer fold at the mantle edge, and weak signals from inner epithelial cells of the same fold, indicating that hic31 is a prismatic-layer matrix protein. Although BLASTP results identify no shared homology with other shell-matrix proteins or any other known proteins, the hic31 tertiary structure is similar to that of collagen I, alpha 1 and alpha 2. It has been well proved that collagen forms the basic organic frameworks in way of collagen fibrils and minerals present within or outside of these fibrils. Therefore, hic31 might be a framework-matrix protein involved in the prismatic-layer biomineralization. Besides, the gene expression of hic31 increase in the early stages of pearl sac development, indicating that hic31 may play important roles in biomineralization of the pearl prismatic layer.

A crucial process: organic matrix and magnesium ion control of amorphous calcium carbonate crystallization on β-chitin film

ACC transformation processes occurring on chitin film mediated by a water soluble matrix or magnesium ions in aqueous solution were investigated.